Iec 61315 2005

NORME INTERNATIONALECEI IEC INTERNATIONAL STANDARD 61315 Deuxième éditionSecond edition2005-10 Etalonnage de wattmètres pour dispositifs à fibres optiques Calibration of fibre-optic po

Organisation

Il convient que le laboratoire d’étalonnage remplisse les exigences de l’ISO/CEI 17025

Il convient d’établir une procédure de mesure détaillée pour chaque type d’étalonnage effectué, donnant des instructions de fonctionnement étape par étape et l’appareillage à utiliser.

Traỗabilitộ

Les exigences de l’ISO/CEI 17025 doivent être remplies

All standards used in calibration must be calibrated according to a detailed program demonstrating their traceability to national standards laboratories or accredited calibration laboratories It is advisable to maintain more than one standard at each level of the hierarchy to verify the operational qualities of the standard through comparison at the same level Ensure that any other testing device significantly influencing calibration results is also calibrated Upon request, specify this testing device and its traceability chain The recalibration periods should be defined and documented.

LICENSED TO MECON Limited - RANCHI/BANGALORE FOR INTERNAL USE AT THIS LOCATION ONLY, SUPPLIED BY BOOK SUPPLY BUREAU.

Figure 2 – Example of a traceability chain

3.36 working standard standard that is used routinely to calibrate or check measuring instruments

NOTE A working standard is usually calibrated against a reference standard

3.37 zero error measurement result of a power meter without irradiation of the optical input port

The calibration laboratory should satisfy requirements of ISO/IEC 17025

There should be a documented measurement procedure for each type of calibration performed, giving step-by-step operating instructions and equipment to be used

The requirements of ISO/IEC 17025 should be met

All calibration standards must be calibrated following a documented program that ensures traceability to national standards laboratories or accredited calibration laboratories It is recommended to maintain multiple standards at each hierarchical level to verify performance through comparisons Additionally, any test equipment that significantly impacts calibration results should also be calibrated, with its traceability chain specified upon request The re-calibration periods must be clearly defined and documented.

Conseils pour les mesures et les étalonnages

Le présent paragraphe donne des conseils d’ordre général pour tous les étalonnages et mesures des wattmètres optiques et pour dispositifs à fibres optiques

Il convient que l’étalonnage soit effectué dans une pièce à température contrôlée si des détecteurs sans régulation de température sont utilisés La température recommandée est de

Humidity control is essential when using optical detectors sensitive to moisture or when condensation on components is a risk Variations in laboratory humidity can alter air absorption, thereby affecting power, particularly between 1,360 nm and 1,410 nm This effect is pronounced during sequential free-space beam calibrations when humidity fluctuates between steps In contrast, for parallel calibrations with approximately equal free-space beam paths, both the reference and measurement device results will change simultaneously, resulting in a negligible impact on calibration outcomes.

Maintaining a clean laboratory is essential for accurate measurements It is important to ensure that connectors and optical input ports are cleaned before taking measurements Additionally, the quality and cleanliness of the connector facing the detector should be verified During measurements, fibers should be moved as little as possible; they can be secured to the test bench if necessary It is advisable to move the sensors towards the fiber rather than the fiber towards the sensor.

It is recommended that the optical source used for exciting the wattmeter be characterized for the central wavelength and spectral bandwidth The spectral bandwidth should be sufficiently narrow to prevent integration over a wide range of wavelengths Additionally, it is advisable to implement measures to ensure the stability of the source, such as independent power control.

Laser diodes are sensitive to back reflections, making it advisable to use an optical attenuator or isolator between the laser diode and the measuring device to enhance stability Additionally, the narrow spectral bandwidths of laser diodes combined with multimode fibers can produce speckle patterns on the optical reference plane, leading to increased measurement uncertainty.

Fiber connectors and adapters can introduce measurement errors due to multiple reflections between the optical input port (or detector) and the connector-adapter combination Therefore, low-reflectivity connectors and adapters are recommended for calibration.

Autrement, un facteur de correction et une incertitude plus importante peuvent devoir être pris en compte

It is recommended to use reference devices with detector diameters of 3 mm or greater, as they can be easily illuminated with a free-space beam and are less prone to contamination from dust or impurities Additionally, it is important to minimize reflections caused by the surface of the reference device If the source emits a divergent beam, using an integrating sphere reference device is advisable.

It is also possible to use devices with flat detectors and apply mathematical correction, which is based on multiplying the far-field distribution emitted by the angular dependence measured by the reference device's detector and integrating over the range of far-field angles.

It is advisable to consider temperature control of detectors for extremely precise calibrations, as these detectors exhibit significant temperature dependencies at certain wavelengths.

4.3 Advice for measurements and calibrations

This subclause gives general advice for all measurements and calibrations of optical and fibre- optic power meters

Calibration should be conducted in a temperature-controlled environment, ideally at 23 °C, especially when using non-temperature-controlled detectors If humidity-sensitive optical detectors are involved, humidity control is essential to prevent condensation on components Variations in laboratory humidity can significantly affect air absorption and, consequently, power measurements, particularly between 1,360 nm and 1,410 nm This effect is pronounced during sequential-type, open-beam calibrations when humidity fluctuates between steps In contrast, parallel-type calibrations with similar open-beam path lengths will yield consistent measurement results for both the reference and test meters, resulting in minimal impact on the overall calibration outcome.

Maintaining a clean laboratory is essential for accurate measurements Always ensure that connectors and optical input ports are thoroughly cleaned prior to use It's important to check the quality and cleanliness of the connector in front of the detector During measurements, minimize movement of all fibers; they can be secured to the workbench if needed Additionally, sensors should be positioned towards the fiber instead of moving the fiber towards the sensor.

The optical source used to excite the power meter must be characterized by its center wavelength and narrow spectral bandwidth to prevent averaging across a wide range of wavelengths Additionally, implementing independent power monitoring can help ensure the stability of the source.

Laser diodes are highly sensitive to back reflections, which can affect their stability To enhance performance, it is recommended to incorporate an optical attenuator or isolator between the laser diode and the test meter Additionally, the narrow spectral bandwidths of laser diodes combined with multimode fiber can generate speckle patterns on the optical reference plane, leading to increased measurement uncertainty.

Fibre connectors and connector adapters can introduce measurement errors due to multiple reflections occurring between the optical input port and the connector-adapter combination To ensure accurate calibration, it is advisable to use connectors and adapters with low reflectivity Failing to do so may necessitate the application of a correction factor and could lead to increased uncertainty in the results.

For optimal performance, it is recommended to utilize reference meters with detector diameters of 3 mm or larger, as they can be effectively irradiated with an open beam and are less prone to contamination from dirt and dust Minimizing surface reflections on the reference meter is crucial In cases where the source emits a divergent beam, employing a reference meter equipped with an integrating sphere is advisable Additionally, using meters with flat detectors is acceptable, provided that mathematical corrections are applied by multiplying the emitted far-field distribution with the measured angle-dependence of the reference meter's detector and integrating across the far-field angles.

Temperature control of the detectors should be considered for highly accurate calibrations, because detectors exhibit strong temperature dependence over some wavelength ranges

Recommandations aux clients

It is advisable for the client (the wattmeter user) to keep at least one reference wattmeter for comparison purposes Such comparisons are crucial before and after sending the device for recalibration, as they help the user determine if the scale has changed, for instance, due to transport when the device is returned Scale changes resulting from adjustments should be monitored closely.

VEI 311-03-16 et VIM 4.30) seront reportés sur le certificat d’étalonnage

Une comparaison régulière des facteurs de correction ou des écarts permettra à l’utilisateur de faire ressortir l’usure excessive et peut-être d’ajuster les intervalles de ré-étalonnage

Calibration of a wattmeter typically involves exposing both the test device and a calibrated reference wattmeter, which has a known uncertainty, to optical radiation The measurement results from the reference device are then transferred to the measuring instrument.

The acceptable spectral bandwidth is determined by the spectral sensitivity of the measuring device; the greater its dependence on wavelength, the narrower the acceptable spectral bandwidth Typical bandwidths are less than 15 nm, which rules out the calibration with LEDs that have a broader bandwidth Therefore, laser diodes or combinations of white light sources and narrowband filters (such as monochromators) are commonly used for the calibration of optical wattmeters.

On peut distinguer, selon le type de source et de géométrie du faisceau d’excitation, quatre méthodes plus fréquentes d’étalonnage:

Tableau 1 – Méthodes d’étalonnage typiques et puissance correspondante

Source de rayonnement Etalonnage à faisceau en espace libre

Etalonnage à faisceau issu d’une fibre ôBlancheằ avec filtre P ≈ 10 àW P ≈ 10 nW à 0,3 àW (MM)

Diode laser P ≈ 10 àW à 1 mW P ≈ 10 àW à 1 mW (SM et MM)

MM: fibre multimodale (en anglais multimode fibre) (généralement fibre à gradient d’indice)

SM: fibre monomodale (en anglais single-mode fibre)

On peut distinguer la méthode de mesure séquentielle et la méthode de mesure parallèle

When calibrating measurement devices, it is essential to maintain a consistent power output from the source, ideally through proper stabilization In parallel calibration, a beam splitter or optical coupler is employed to simultaneously excite both the reference device and the measuring device It is crucial to accurately determine the ratio of the beam splitter or optical coupler and to assess its stability.

For example, Figure 3 illustrates a measurement setup for sequential calibration using a beam from a fiber The setup includes an injection device designed to suppress cladding modes and create an appropriate modal excitation.

To ensure accuracy, it is advisable for users of power meters to maintain at least one reference meter for comparison This practice is crucial, especially before and after sending the meter for re-calibration, as it helps users assess any potential scale changes that may occur during transport Monitoring these comparisons allows for the detection of adjustments that could affect measurement reliability.

VIM 4.30) will be reported on the calibration certificate

A regular comparison of the correction factors, or of the deviations, will allow the user to screen out excessive ageing, and to possibly adjust the recalibration intervals

Calibrating a power meter involves comparing it with a reference meter that has a known uncertainty This process requires exposing both the test meter and the calibrated reference meter to optical radiation, allowing the measurement results from the reference meter to be transferred to the test meter.

The spectral bandwidth that can be used is determined by the spectral responsivity of the test meter, with stronger wavelength dependence leading to narrower bandwidths Typically, bandwidths are less than 15 nm, which limits the calibration options to narrower sources As a result, laser diodes or combinations of "white" light sources with narrow-bandwidth filters, such as monochromators, are commonly employed for calibrating optical power meters.

Depending on the type of source and the exciting beam geometry, four most frequent calibration methods can be distinguished:

Table 1 – Typical calibration methods and correspondent power

Radiation source Open-beam calibration Fibre beam calibration

"White" with filter P ≈ 10 àW P ≈ 10 nW to 0,3 àW (MM)

Laser diode P ≈ 10 àW to 1 mW P ≈ 10 àW to 1 mW (SM and MM)

MM: multimode fibre (usually graded-index fibre)

There are two primary measurement methods: sequential and parallel In the sequential method, both the reference meter and test meter are exposed to the source one after the other, requiring the radiated power to be stabilized to maintain consistency Conversely, the parallel calibration method utilizes a beam splitter or branching device to simultaneously excite both meters It is crucial to accurately determine the ratio of the beam splitter or branching device and to assess its stability for reliable measurements.

As an example, a measurement setup for sequential, fibre-based calibration is illustrated in

Figure 3 A launching device, for removal of the cladding modes and creation of an appropriate modal excitation, is included in the setup

Figure 3 – Montage de mesure pour un étalonnage séquentiel, utilisant le faisceau issu d’une fibre

Etablissement des conditions d’étalonnage

Calibration conditions refer to the measurement conditions during the calibration process Establishing and maintaining these conditions is crucial, as any changes can lead to inaccurate measurement results It is advisable for calibration conditions to closely approximate the desired operating conditions, ensuring that uncertainty is minimized.

In a functioning environment, it is essential to keep supplementary conditions as low as possible Calibration conditions should be defined using nominal values with uncertainties when necessary To comply with the current standard, calibration conditions must include at least: a) the calibration date, b) ambient temperature with uncertainty, for example, 23 °C ± 1 °C, c) ambient relative humidity if it has an impact; otherwise, a relative humidity below the condensation point is assumed, d) the nominal radiant power at the optical reference plane, and e) the beam geometry.

A free-space beam, such as a collimated beam, is characterized by the spot diameter on the optical reference plane, the numerical aperture of the beam, and the distribution of energy illumination within the beam Typical energy illumination distributions include uniform, Gaussian, and even irregular patterns, which may exhibit speckles.

The type of fiber and, if applicable, its degree of excitation (e.g., total excitation) are crucial factors Additionally, the connector-adapter combination, including the type of connector, polishing, and adapter, plays a significant role in the excitation source It is important to specify the central wavelength of the excitation source along with its uncertainty, as well as the spectral bandwidth of the excitation source and its associated uncertainty Furthermore, the state of polarization must be identified, whether it is unpolarized light or polarized light, with the option of an undefined state If the latter is selected, the uncertainty due to polarization-dependent response should be considered in sections 5.3.2 and 5.3.4.

It is important to note that the aforementioned conditions are not exhaustive There may be additional factors that significantly influence calibration uncertainty, and these should also be acknowledged.

For free-space calibration, it is advisable to illuminate the optical reference plane of the wattmeter at the center with a beam diameter smaller than the active surface of the optical reference plane.

(optional) Power meter under test

Figure 3 – Measurement setup for sequential, fibre-based calibration

The calibration conditions are the measurement conditions during the calibration process

Establishing and maintaining proper calibration conditions is crucial, as any alterations can lead to inaccurate measurement results These conditions should closely resemble the intended operating environment to minimize additional uncertainty Calibration conditions must be documented with nominal values and associated uncertainties, including: a) the calibration date; b) ambient temperature (e.g., 23 °C ± 1 °C); c) ambient relative humidity, if relevant, or a humidity below the condensation point; d) nominal radiant power on the optical reference plane; and e) beam geometry.

An open beam, such as a collimated beam, is characterized by its spot diameter on the optical reference plane, numerical aperture, and the distribution of irradiance Common irradiance distributions include uniform, Gaussian, and irregular patterns.

The article discusses several key factors related to fiber optics, including the type of fiber and its degree of excitation, such as whether it is fully excited It also addresses the connector-adapter combination, detailing the connector type, polishing, and adapter associated with the exciting source Additionally, it highlights the importance of the center wavelength of the exciting source along with its uncertainty, as well as the spectral bandwidth and its uncertainty Finally, it specifies the state of polarization, distinguishing between "unpolarized light" and "polarized light, undefinite state," noting that if the latter is selected, the uncertainty from polarization-dependent response must be considered in sections 5.3.2 and 5.3.4.

The above conditions may not be exhaustive There may be other parameters which have a significant influence on the calibration uncertainty and therefore shall be reported, too

For effective calibration using an open-beam method, it is essential that the optical reference plane of the power meter is illuminated centrally by a beam with a diameter that is smaller than the active area of the optical reference plane.

When calibrating with a fiber, both single-mode and multimode fibers can be utilized Single-mode fibers offer reproducible beam characteristics but may not be available for all wavelengths In contrast, multimode fibers are preferred for total excitation due to their easier reproducibility An injection device may be required to generate the appropriate excitation It's important to note that multimode fibers can produce irregular beam distributions (speckle patterns) when driven by a laser diode, leading to increased calibration uncertainty If necessary, it is advisable to remove the optical power from the cladding modes using a mode extractor or suitable injection device.

It is advisable to use a connector-adapter combination only if the wattmeter is calibrated with a fiber, rather than with a free-space beam Additionally, it is recommended to select a connector and adapter combination that exhibits sufficiently low reflections towards the wattmeter.

Procédure d'étalonnage

(1) Etablir et enregistrer les conditions d’étalonnage appropriées (5.1) Mettre tous les appareils sous tension et attendre suffisamment de temps pour qu’ils se stabilisent

Adjust the settings of both the reference and measurement devices according to the user manual Set the wavelength on all devices to match the source wavelength and select the appropriate power ranges.

Enregistrer les ô modes d’appareil ằ des deux wattmốtres Rộgler le zộro des deux appareils, si nécessaire

To measure optical power using the reference device P std,1, multiply the measurement result by the correction factor FC std specified in its calibration certificate, provided it has not been adjusted.

FC variation calculé en 5.3.3 si nécessaire Enregistrer le résultat de mesure, P réf,1 =

P std,1 × FC std × FC variation Il s’agit de la meilleure estimation de la vraie puissance

(4) Mesurer la puissance optique avec l’appareil de mesure Appliquer les corrections nécessaires, comme le suggèrent les instructions de fonctionnement Enregistrer le résultat de mesure, P DEE,1

(5) Calculer le premier d’une série de facteurs de correction:

(6) Répéter les étapes (3) à (5) plusieurs fois dans le but d’obtenir plusieurs facteurs de correction, FC comparaison,1 à FC comparaison,n

(7) Calculer et enregistrer le facteur de correction moyen, FC DEE à partir des facteurs de correction individuels:

Si on le souhaite, l’écart D peut être calculé à partir du facteur de correction:

In future use of the measuring device, measurement results must be multiplied by the FC DEE Alternatively, the device can be adjusted so that the correction factor is set to 1 In this case, it is important to repeat the comparison for verification.

In calibration processes involving optical fibres, both single-mode and multimode fibres can be utilized Single-mode fibres offer consistent beam characteristics but may not be suitable for all wavelengths Conversely, multimode fibres are preferred for full excitation, as this can be more easily replicated A launching device may be required to achieve the desired excitation However, it's important to note that multimode fibres can produce irregular beam patterns, known as speckle patterns, when powered by a laser diode, leading to increased calibration uncertainty To minimize this uncertainty, any optical power in the cladding, or cladding modes, should be eliminated using an appropriate mode stripper or launching device.

For accurate reporting, a connector-adapter combination should only be used when the power meter is calibrated with a fiber, rather than an open beam It is advisable to select a connector and adapter combination that minimizes reflections back to the power meter.

(1) Establish and record the appropriate calibration conditions (5.1) Switch on all instrumentation and wait for enough time to stabilize

To ensure accurate measurements, configure the reference and test meters according to the instruction manual, setting the wavelength to match the source wavelength and selecting suitable power ranges Document the instrument states for both meters and, if necessary, adjust their zero settings.

To accurately measure optical power, use the reference meter P std,1 and multiply the result by the calibration correction factor CF std from its certificate, if no adjustments have been made If necessary, also apply the correction factor CF change as calculated in section 5.3.3 The final measurement result, expressed as P ref,1 = P std,1 x CF std x CF change, provides the best estimate of the true optical power.

(4) Measure the optical power with the test meter Apply necessary corrections as suggested by the operating instructions Record the measurement result, P DUT,1

(5) Calculate the first of a series of correction factors:

(6) Repeat steps (3) through (5) several times, with the result of obtaining several correction factors, CF comparison,1 to CF comparison,n

(7) Calculate and record the average correction factor, CF DUT from the individual correction factors:

If desired the deviation D can be calculated from the correction factor:

In later use of the test meter, the measurement results shall be multiplied with CF DUT

Alternatively, an adjustment of the test meter can be made so that the correction factor is changed to 1 In this case, the comparison should be repeated for verification

Incertitude d’étalonnage

L’incertitude d’étalonnage est l’incertitude de mesure du facteur de correction FC DEE Calculer l’incertitude type combinée à partir de:

(FC u u u u = + + (4) ó u montage = incertitude due au montage, (5.3.1); u réf = incertitude de l’appareil de référence, (5.3.2); u DEE = incertitude due à l’appareil de mesure, (5.3.4)

The equation (4) is only valid when the input variables are independent or uncorrelated If any input variables are significantly correlated, this correlation must be considered For more details, refer to the GUM.

Calculer ensuite l’incertitude étendue à partir de:

U = × , (5) ó k est le facteur de recouvrement Voir l’Annexe A pour plus de précisions

The uncertainties arising from the setup include: a) Uncertainty due to the power instability of the source, where a laser source may exhibit intrinsic variations in output power over time and respond inconsistently to changes in retro-reflections and the polarization state of the reflected light b) Uncertainty related to the beam splitter or optical coupler ratio (for the parallel method), which may depend on polarization c) Additionally, depending on the setup and method used, other uncertainties may need to be considered.

The instability in the power of the source, the beam splitter ratio, or the optical coupler (for the parallel method) leads to variability in the measurement of the correction factor The uncertainty arising from these instabilities can be calculated using the experimental standard deviation of the correction factors FC comparison,1 to FC comparison,n measured during calibration (Equation (1)) It is important to have a large number of comparisons to minimize this uncertainty For more details on the evaluation of Type A uncertainty, refer to Appendix A.

FC u s( comparaiso n ) typeA montage, = (6) ó s(FC comparaison) est l’écart type expérimental des facteurs de correction; n est le nombre de cycles de mesures au cours du processus d’étalonnage

The calibration uncertainty is the measurement uncertainty of the correction factor CF DUT

Calculate the combined standard uncertainty from:

CF u( )= + + (4) where u setup = uncertainty due to the setup, (5.3.1); u ref = uncertainty of the reference meter, (5.3.2); u DUT = uncertainty due to the test meter, (5.3.4)

Equation (4) is applicable solely when the input quantities are independent or uncorrelated In cases where certain input quantities exhibit significant correlation, it is essential to consider this correlation For further details, refer to the GUM.

Then calculate the expanded uncertainty from:

U = × , (5) where k is the coverage factor See Annexe A for more detail

5.3.1 Uncertainty due to the setup

The setup may introduce several uncertainties, including a) instability in the source power, which can fluctuate due to intrinsic variations and reactions to back-reflections and changes in the polarization state of reflected light; b) uncertainties arising from the beam splitter or branching device ratio, particularly in parallel methods, which may be affected by polarization dependence; and c) additional uncertainties that may need to be considered based on the specific setup and method used.

Instabilities in the source power and the beam splitter or branching device ratio can lead to variations in the measurement of the correction factor The uncertainty arising from these instabilities can be quantified using the experimental standard deviation of the correction factors, CF comparison,1 to CF comparison,n, obtained during the calibration process.

(1)) The number of comparisons should be large to reduce this uncertainty See Annex A for more detail on type A evaluation of uncertainty n

CF u s( comparison ) typeA setup, = (6) where: s(CF comparison ) is the experimental standard deviation of the correction factors; n is the number of measurement cycles during the calibration process

Cette incertitude peut également être calculée à partir d’un écart type évalué une fois à partir des mesures et utilisé pour tous les étalonnages ou à partir d’une évaluation de type B

It is essential that the instability remains consistent across different calibrations and is not dependent on the measuring device The variable $ n $ in Equation (6) consistently denotes the number of measurement cycles during the current calibration process.

The Type A evaluated uncertainty will also be influenced by the repeatability of the connection, whether through a sequential measurement method or slight modifications in measurement conditions during the calibration process It may partially account for certain uncertainties related to the reference device or the measuring instrument It is essential to ensure that uncertainty components are neither counted twice nor overlooked.

Calculer l’incertitude due au montage en combinant toutes les incertitudes partielles décrites dans le présent paragraphe:

5.3.2 Incertitude de l’appareil de référence

L’incertitude de l’appareil de référence est principalement due à son étalonnage, aux incertitudes des conditions d’étalonnage actuelles et à la dépendance de l’appareil de référence par rapport à ces conditions

The following uncertainties must be assessed: the evaluation can be based on measurements, estimates, or a combination of both The calculation of uncertainties is detailed in Annex A, while the measurement of dependence on conditions is described in section 6.2.1 a) Calibration uncertainty of the reference device should be obtained from its calibration certificate b) Uncertainty due to changes in the conditions under which the reference device was calibrated and the current calibration conditions is calculated in section 5.3.3 c) Uncertainty related to the temperature dependence of the reference device d) Uncertainty due to the relative humidity dependence of the reference device.

Integrating sphere wattmeters are highly sensitive to water absorption peaks when using narrow laser sources Uncertainties arise from the beam geometry dependence of the reference device, as well as from multiple reflections that can occur between the optical input port and the radiation source, such as in connector-adapter combinations, which can alter the measured power Additionally, uncertainties are influenced by the wavelength dependence of the reference device, the spectral bandwidth of the source, and the polarization state of the reference device, unless unpolarized or depolarized light is used for calibration Optical interference can also introduce uncertainties, with Fabry-Perot cavities potentially forming between the detector surface, the window, and the connector end, if utilized.

Uncertainty can be quantified using a standard deviation derived from initial measurements, applicable across all calibrations, or through a type B evaluation Consequently, the instability should remain relatively consistent between calibrations and should not be influenced by the test meter used.

The number n in Equation (6) is always the number of measurement cycles during the current calibration process

Type A evaluated uncertainty is affected by the repeatability of connections in sequential measurement methods and minor variations in measurement conditions during calibration It may partially consider uncertainties related to the reference meter and test meter It is crucial to avoid double-counting uncertainty components while ensuring none are overlooked.

Calculate the uncertainty due to the setup by combining all partial uncertainties described in this subclause:

5.3.2 Uncertainty of the reference meter

The uncertainty of a reference meter primarily arises from its calibration process, the variability in current calibration conditions, and the meter's dependence on these conditions.

The evaluation of uncertainties can be based on measurements, estimations, or a combination of both, as detailed in Annex A Key uncertainties include: a) calibration uncertainty from the reference meter's calibration certificate; b) changes in conditions from calibration to current conditions; c) temperature dependence; d) relative humidity effects, particularly for power meters with integrating spheres; e) beam geometry dependence; f) multiple reflections between the optical input port and radiation source; g) wavelength dependence; h) source spectral bandwidth dependence; i) state of polarization dependence, unless unpolarized light is used; and j) optical interference, which may occur in Fabry-Perot cavities between the detector surface and connector.

The document is licensed to MECON Limited for internal use in Ranchi and Bangalore, provided by the Book Supply Bureau It discusses the uncertainty related to the resolution of the reference device, indicating that if the resolution is denoted as \$\delta y_{\text{ref}}\$ the standard uncertainty can be derived from the guidelines in the GUM, specifically section F.2.2.1.

Compte-rendu des résultats

Calibration results must be documented in accordance with ISO/IEC 17025 Calibration certificates or reports referencing this standard should include the following essential information: a) All calibration conditions as outlined in section 5.1; b) Correction factors or deviations of the measuring device if it has not been adjusted; c) Correction factors or deviations at receipt and after adjustment, if applicable; d) Calibration uncertainty presented as an expanded uncertainty, as described in section 5.3; e) The mode of the measuring device during calibration; f) Evidence that measurements are recordable (refer to ISO/IEC 17025:1999, section 5.10.4.1 c)).

6 Incertitude de mesure d’un wattmètre étalonné

L’incertitude de mesure d’un wattmètre étalonné est supérieure à son incertitude d’étalonnage

Il s’agit de la combinaison de l’incertitude d’étalonnage et des contributions d’incertitude dues à la dépendance du wattmètre par rapport aux conditions de mesure

La détermination de l’incertitude de mesure d’un wattmètre étalonné utilisé aux conditions de référence ou aux conditions de fonctionnement ne fait pas partie du processus d’étalonnage

It is produced, for instance, by wattmeter manufacturers to establish specifications Compliance with this standard is not mandatory for calibration certificates or calibration reports that reference it.

Incertitude aux conditions de référence

Reference conditions are utilized for the performance testing of wattmeters or for making comparisons Typically defined by manufacturers, these conditions specify the smallest measurement uncertainty of a device; thus, they often align closely with the calibration conditions.

The uncertainty at reference conditions refers to the uncertainty in the measurement result obtained from a calibrated and adjusted wattmeter when operating under reference conditions This uncertainty is influenced by the calibration uncertainty of the wattmeter, the reference conditions, and the wattmeter's dependence on these conditions Consequently, the uncertainty at reference conditions is always greater than the calibration uncertainty Even when the reference conditions match the calibration conditions, any dependencies of the wattmeter under test relative to the reference conditions must be added again (in quadrature) to the calibration uncertainty Calculating the uncertainty at reference conditions for the calibrated measuring device is akin to determining the measurement uncertainty under the calibration conditions of the reference device as described in section 5.3.2.

The calibration uncertainty of the measuring device, denoted as \$u(FC DEE)\$, is determined based on equation (25) This uncertainty, \$u DEE\$, arises from the device's dependence on reference conditions, as outlined in section 5.3.4.

Il convient que la description des conditions de rộfộrence soit effectuộe de la mờme faỗon que les conditions d’étalonnage décrites en 5.1

Calibration results must be reported in accordance with ISO/IEC 17025, including essential information such as calibration conditions, correction factors or deviations of the test meter, and calibration uncertainty expressed as expanded uncertainty Additionally, the report should detail the instrument's state during calibration and provide evidence of measurement traceability.

6 Measurement uncertainty of a calibrated power meter

The measurement uncertainty of a calibrated power meter exceeds its calibration uncertainty, as it encompasses both the calibration uncertainty and additional uncertainty contributions arising from the measurement conditions.

The measurement uncertainty of a calibrated power meter, whether under reference or operating conditions, is not included in the calibration process This assessment is typically conducted by power meter manufacturers to define specifications However, it is not a requirement for calibration certificates or reports associated with this standard.

Reference conditions are essential for evaluating the performance of power meters and conducting intercomparisons Typically defined by manufacturers, these conditions aim to establish the minimum uncertainty of a measuring instrument, often aligning closely with its calibration conditions.

The uncertainty at reference conditions refers to the measurement uncertainty of a calibrated power meter when it operates under specified reference conditions This uncertainty is influenced by the calibration uncertainty of the power meter, the specific reference conditions, and the meter's sensitivity to these conditions Consequently, the uncertainty at reference conditions is always greater than the calibration uncertainty Even if the reference conditions match the calibration conditions, the power meter's dependencies on these conditions must be considered, requiring an additional calculation of uncertainty in quadrature Thus, determining the uncertainty at reference conditions for the calibrated test meter parallels the process of calculating measurement uncertainty at calibration conditions for the reference meter.

2 DUT DUT ions 2 ref_condit

The calibration uncertainty of the test meter, denoted as $ u(CF \, DUT) $, is calculated according to section 5.3, while the uncertainty associated with the test meter's dependence on reference conditions, represented as $ u \, DUT $, is determined from section 5.3.4 The overall uncertainty can be expressed as $ u \, CF \, u \, u = ( ) + (25) $.

The description of the reference conditions should be made in the same way as the calibration conditions described in 5.1

Incertitude aux conditions de fonctionnement

L’incertitude aux conditions de fonctionnement (ou incertitude de fonctionnement CEI 60359,

The uncertainty in the measurement result obtained from a calibrated and adjusted wattmeter is influenced by various factors, including calibration uncertainty, operating conditions, and the wattmeter's dependence on these conditions.

The calibration uncertainty of the measuring device, denoted as \$u(FC DEE)\$, is determined from Equation (26) Additionally, the extension uncertainty, \$u_{extension}\$, arises from the device's dependence on operational conditions, as outlined in Equation (27).

Unlike the calibration conditions outlined in section 5.1, each operating condition should ideally be described by a range The complete set of operating conditions is defined by: a) the maximum time interval between recalibrations; b) the range of ambient temperatures; c) the range of power levels (measurement range); d) the range of beam geometries characterized by their spot diameter and numerical aperture, or the range of fiber types; e) any applicable connector-adapter combinations; f) the range of wavelengths of the source; g) the maximum spectral bandwidth of the source.

Tous les états de polarisation possibles sont inclus par défaut dans les conditions de fonctionnement On considère également qu’il y a une humidité relative en dessous du point de condensation

Les conditions ci-dessus peuvent être définies soit par le fabricant du wattmètre, soit par le centre d’étalonnage en charge de l’étalonnage pour les conditions de fonctionnement

Pour calculer l’incertitude d’extension, combiner toutes les incertitudes dues aux dépendances par rapport aux conditions:

2 i extension, extension (27) ó u extension,i sont les contributions à l’incertitude d’extension; n est le nombre total de contributions

6.2.1 Détermination des dépendances par rapport aux conditions

It is advisable to record each individual dependency as a relative change in the device's response, triggered by modifications in the corresponding operating conditions During testing, it is essential to maintain all other conditions at calibration settings The zero point is determined by the response to these calibration conditions Consequently, each dependency can be specified by a range defined by the maximum positive and negative variations in response Typically, an asymmetric range near the zero point is observed, as illustrated in Figure 5.

Operating uncertainty, as defined in section 2.2.11 of IEC 60359, refers to the measurement uncertainty of a calibrated power meter when used under varying operating conditions This uncertainty is influenced by calibration accuracy, the specific operating conditions, and the power meter's sensitivity to these conditions.

The calibration uncertainty of the test meter, denoted as $ u(CF \, DUT) $, is calculated according to section 5.3, while the extension uncertainty, which arises from the meter's dependence on operating conditions, is determined using Equation (27).

Each operating condition should be defined by a range whenever possible, in contrast to the calibration conditions outlined in section 5.1 The specified operating conditions include: a) the maximum interval between recalibrations; b) the range of ambient temperatures; c) the measuring range of power levels; d) the variations in beam geometries characterized by spot diameter and numerical aperture, or different types of fibers; e) any applicable connector-adapter combinations; f) the range of source wavelengths; and g) the maximum spectral bandwidth of the source.

All possible polarization states are included in the operating conditions by default A relative humidity below the condensation point is also assumed

The above conditions may be defined either by the power meter manufacturer or by the calibration laboratory in charge of the calibration for operating conditions

To calculate the extension uncertainty, combine all uncertainties due to the dependences on the conditions:

2 i extension, extension (27) where: u extension,i are contributions to the extension uncertainty; n is the total number of contributions

6.2.1 Determination of dependences on conditions

Each individual dependence must be documented as the relative change in the meter's response due to variations in relevant operating conditions, while maintaining all other conditions at calibration levels The zero point is established based on the response under these calibration conditions Consequently, each dependence is characterized by a range defined by the maximum positive and negative response changes, often resulting in an asymmetric range around the zero point, as illustrated in Figure 5.

Gamme définie du paramètre de fonctionnement

Dépendance à la condition de fonctionnement x i

Figure 5 – Détermination et enregistrement d’une incertitude d’extension

To achieve accurate measurement precision, it is advisable to adhere to the guidelines outlined in Article 4 It is essential to minimize measurement uncertainties, as the results must account for these uncertainties Estimations may be utilized in place of direct measurements, provided they are grounded in known physical relationships or based on a sufficiently large number of characteristic measurements from the same type of measuring device.

To determine the combined standard uncertainty of the measuring device under operating conditions, the limits quantifying individual dependencies must be converted into standard uncertainties using Equation (A.6).

Individual uncertainties are generally considered to be independent However, in certain cases, an uncertainty may be significantly dependent on multiple conditions Examples of this can be found in sections 6.2.4, 6.2.6, and 6.2.7 If the extension uncertainty increases after modifying other conditions (with their defined operating ranges), this heightened uncertainty must be recorded Consequently, the calculation of uncertainty should be based on these increased uncertainties.

Aging refers to the change in response over a period of time It can be assessed through successive calibrations of the device under the same conditions or based on the manufacturer's specifications.

For a manufacturer, the change in response over time must be assessed under the assumption of careful device usage It is advisable to expose the wattmeter to its typical environmental conditions, such as ambient temperature.

For laboratory-type devices, it is recommended to maintain a temperature of (23 ± 1) °C with an unlit optical input, operating in continuous cycles of 12 hours on and 12 hours off, totaling a testing period equal to the cycle duration It is essential to measure response changes by comparing with a working standard Regular and recordable recalibration of the working standard is necessary to mitigate aging effects Additionally, measurement uncertainty, particularly that of the working standard, must be considered.

It is advisable to calculate aging uncertainty using a rectangular distribution as outlined in Article A.2 For instance, if a detector is known to increase its response by a maximum of 0.1% per year at a specific wavelength, the aging uncertainty is represented by a rectangle extending from 0% at time zero to +0.1% at one year.

Specified range of operating parameter

Figure 5 – Determining and recording an extension uncertainty

In order to obtain good measurement accuracy, the guidelines in Clause 4 should be observed

Tiêu đề	IEC 61315 2005
Trường học	MECON Limited
Chuyên ngành	Calibration of fibre-optic power meters
Thể loại	Standards
Năm xuất bản	2005
Thành phố	Ranchi/Bangalore

Định dạng
Số trang	94
Dung lượng	0,97 MB