An approach towards a singlemode local loop is presented in which each customer is given a dedicated wavelength channel by taking different wavelength slices from identical LEDs. This is accomplished by means of wavelength division multiplexing (WDM) components. Results from a fourchannel system operating at 2 Mbits over 2.2 km, together with a theoretical analysis of a tenchannel system, are presented Published in: Electronics Letters (Volume:24 , Issue: 7 ) Page(s): 389 390 ISSN : 00135194 INSPEC Accession Number: 3151136 long haul specifications for distances between 6 and 11 km (Table 2). The bit error rate of the DS1 data stream was measured and found to be better than Table 2 VIDEO PERFORMANCE MEASUREMENTS No. of video No. of DS1 Length channels channels SNR DG DP km % deg 0 1 0 67.0 1.9 0.5 6 1 1 62.0 1.8 1.2 6 2 1 61.0 1.8 1.05 11 1 1 57.0 1.2 1.9 11 2 1 56.0 4.8 33 Acknowledgments: We acknowledge the assistance of L. Curtis, R. E. Spicer, P. W. Shumate and C. W. Lundgren, all of Bellcore, and J. Koscinski and M. Eros of General Optron ics Corp. for their assistance during this study. P. S. VENKATESAN P. S. NATARAJAN J. OROST Bell Communications Research 331 Newman Springs Road Red Bank, NJ 077017020, USA 4th February 1988 References OLSEN, G. H. : ‘Long wavelength LEDs, a challenge to laser diodes’, Photonics Spectra, 1985, 17, pp. 121124 PERSONICK, s. D. : ‘Fiber optics: technology and applications’ (Plenum Press, New York, 1985) SHUMATE, P. w., et al.: ‘Transmission of 140Mbs signals over single mode fiber using surface and edgeemitting 1.3pm LEDs’, Electron. Lett., 1985, 21, pp. 522524 WAKABAYASKI, T., KIHARA, T., and MURASE, T.: ‘4590135 Mbits optical fiber transmission system’, Fujitsu Sci. d? Tech. J., 1985, 21, CIMLETT, J. L., et a.: ‘Dispersion penalties for single mode fiber transmission using 1.3 and 1.5pm LEDs’, Electron. Lett., 1985, 21, pp. 21 1223 pp. 668670 TANIFUII, T., MATSUURA, M., and YAMAMOTO, Y.: ‘42km analogue video signal transmission in single mode fibers using 1.3 pm edge emitting LEDs’, Electron. Lett., 1986, 22, pp. 192193 POPHILLAT, L.: ‘Video transmission using a 1.3pm LED and monomode fiber’. Proc. 10th ECOC, Stuttgart, Germany, Septem ber 1984, pp. 238239 Electrical Performance Standards for Television Relay Facilities, EIA Standard RS250B, Sep., 1976, Electronic Industries Associ ation, 2001, I Street, N.W., Washington, D.C. 20006, USA Preliminary generic requirements for PFM video and data trans mission on single mode fiber, Bell Communications Research Technical Advisory, TATSY000384, April 1986, obtainable from Information Manager, 435 South Street, Room 27147, Morris town, NJ 07960, USA LED SPECTRAL SLICING FOR SING LEM 0 DE LOCAL LOOP APPLICATIONS Indexing terms: Optical communications, Networks, Multi plexing, Optical fibres An approach towards a singlemode local loop is presented in which each customer is given a dedicated wavelength
Trang 1long haul specifications for distances between 6 and 11 km
(Table 2) The bit error rate of the DS1 data stream was
measured and found to be better than
Table 2 VIDEO PERFORMANCE MEASUREMENTS
No of video No of DS1
Length channels channels SNR D G D P
A c k n o w l e d g m e n t s : We acknowledge the assistance of L
Curtis, R E Spicer, P W Shumate and C W Lundgren, all
of Bellcore, and J Koscinski and M Eros of General Optron-
ics Corp for their assistance during this study
P S VENKATESAN
P S NATARAJAN
J OROST
Bell Communications Research
331 Newman Springs Road
Red Bank, NJ 07701-7020, U S A
4th February 1988
References
OLSEN, G H : ‘Long wavelength LEDs, a challenge to laser diodes’,
Photonics Spectra, 1985, 17, pp 121-124
PERSONICK, s D : ‘Fiber optics: technology and applications’
(Plenum Press, New York, 1985)
SHUMATE, P w , et al.: ‘Transmission of 140Mb/s signals over
single mode fiber using surface and edge-emitting 1.3pm LEDs’,
Electron Lett., 1985, 21, pp 522-524
WAKABAYASKI, T., KIHARA, T., and MURASE, T.: ‘45/90/135 Mbit/s
optical fiber transmission system’, Fujitsu Sci d? Tech J , 1985, 21,
CIMLETT, J L., et a / : ‘Dispersion penalties for single mode fiber
transmission using 1.3 and 1.5pm LEDs’, Electron Lett., 1985, 21,
pp 21 1-223
pp 668-670
TANIFUII, T., MATSUURA, M., and YAMAMOTO, Y : ‘42km analogue
video signal transmission in single mode fibers using 1.3 pm edge-
emitting LEDs’, Electron Lett., 1986, 22, pp 192-193
POPHILLAT, L : ‘Video transmission using a 1.3pm LED and
monomode fiber’ Proc 10th ECOC, Stuttgart, Germany, Septem-
ber 1984, pp 238-239
Electrical Performance Standards for Television Relay Facilities,
EIA Standard RS-250B, Sep., 1976, Electronic Industries Associ-
ation, 2001, I Street, N.W., Washington, D.C 20006, USA
Preliminary generic requirements for PFM video and data trans-
mission on single mode fiber, Bell Communications Research
Technical Advisory, TA-TSY-000384, April 1986, obtainable from
Information Manager, 435 South Street, Room 27-147, Morris-
town, NJ 07960, USA
LED SPECTRAL SLICING FOR
Indexing terms: Optical communications, Networks, Multi-
plexing, Optical fibres
An approach towards a single-mode local loop is presented
in which each customer is given a dedicated wavelength
channel by taking different wavelength slices from identical
LEDs This is accomplished by means of wavelength division
multiplexing (WDM) components Results from a four-
channel system operating at 2 Mbit/s over 2.2 km, together
with a theoretical analysis of a ten-channel system, are pre-
sen ted
Introduction: Passive optical fibre local loop networks have
recently received much A key feature of such
networks is cost reduction achieved by sharing fibre amongst
a number of subscribers However, those employing wave-
length division multiplexing (WDM) typically require lasers selected within particular wavelength ranges which greatly increases costs and system design complexity
This letter describes a method which gives each subscriber a dedicated wavelength channel by taking a different wave- length slice for each subscriber from identical LEDs using WDM components sited in street mounted distribution points (DP) This approach is based on that first suggested for LAN applications in Reference 3, but uses single-mode fibre throughout A four channel system has been demonstrated using readily available components, with theoretical results obtained for a ten channel system
Key features of the system are:
(i) All subscribers’ LEDs are identical
(ii) All wavelength selective components are identical (iii) Subscribers have a dedicated wavelength channel for narrow or broadband use
(iv) Single-mode fibre between distribution points and central ofice is shared to reduce costs
S y s t e m configuration: The system is shown in Fig 1 and Table
1 The four low-cost 2 Mbit/s digital transmission systems were based on those currently in use in the British Telecom
n e t ~ o r k , ~ but modified to operate with 1300 nm ELED trans- mitters and a recently developed high-sensitivity receiver.’ The multichannel WDM multiplexers were of a prism/grating design6 having FWHM channel widths of 3.65 nm centred on wavelengths of 1270, 1290, 1310 and 1330nm FC single-mode connectors were used for all connections, these being fusion spliced to the WDM device input/output fibres (Fig 1)
central I
office I d ’ 5 ~ ~ ~ ’ 0 7 subscriber
Fig 1 Schematic diagram of the spectral slicing system
connector
x splice 2.2 km of single-mode fibre having a connector to connector loss of 2.4dB (including 2 splices), was employed to simulate a typical head oflice to distribution point link
System r e s u l t s : With typical launch powers from the com- mercially available ELEDs of - 25 dBm (single-mode fibre) and receiver sensitivity of - 56.5 dBm ( BER) the system configured as described operated with zero errors on all four channels Excess losses of 4 and 5dB were measured for the multiplexer and demultiplexer respectively, with channel to channel crosstalk isolation of > 41 dB
As each channel of the transmission system takes a slice from the total LED output spectrum and hence optical power, there is also an apparent loss in the multiplexers due to the
Table 1 SUMMARY O F SYSTEM DETAILS
Launch power - 25 dBm Centre wavelength 1300 nm Spectral width 63 nm (FWHM)
Line rate, code
2 Mbit/s, HDB3
(10-9 BER)
Trang 2slicing operation, which we have termed distribution loss
With the four channel system the theoretical analysis predict-
ed distribution losses in the range 13-15dB, these figures
showing good agreement with the measured values of 13-
16dB The worst case system power budget is summarised in
Table 2
DEMONSTRATION SYSTEM
LED launch power
Multiplexer distribution
Multiplexer excess loss
Demultiplexer excess loss
Fibre and splice loss
Receiver sensitivity
Marain
- 26.7
- 16
4
5
2.4
- 56.5 2.4
dBm
dB
dB
dB
dB dBm
dB
T h e o r e t i c a l a n a l y s i s : In the UK network the average loop
length is ~2 km with ten subscribers to a distribution point,
giving a useful target for our system A theoretical model of
the distribution loss has been developed assuming Gaussian
channel s p a c i n g , n m
Fig 2 Theoretical ten-channel distribution loss
-a- channel 1 and 10
+ channel 2 and 9
-0- channel 3 and 8
-0- channel 4 and 7
-.- channel 5 and 6
FWHM of LED = 90nm
Crosstalk attenuation = 15 dB
shapes for the LED spectrum and that of the WDM channel Optimised results for distribution losses against channel spacing assuming an LED spectral width of 90nm and a fixed crosstalk isolation of 15dB are shown in Fig 2 A channel spacing of lOnm results in a worst-case distribution loss of 15dB It is therefore evident that a 90nm LED and an opti- mised channel spacing in the WDM device can give a power budget for ten channels equivalent to that of our demonstra- tion system
Conclusions: In conclusion, an approach to cost-effective deployment of single-mode fibre in the local loop has been demonstrated using spectral slicing of LEDs for narrowband working Readily available components were used to produce
a four channel system Theoretical analysis predicts a similar power budget for a ten channel system given optimised devices
A c k n o w l e d g m e n t s : The authors would like to thank the Direc-
tor of Research and Technology BTRL and the General Manager of BT Network Systems for permission to publish this letter
M H REEVE
A R HUNWICKS
W ZHAO
S G METHLEY
L BICKERS
S HORNUNG
British Telecom Research Laboratories Martlesham Heath
Ipswich IPS 7RE, United Kingdom
4th February 1988
References TOKURA, N., et al.: ‘Broadband subscriber network using optical star couplers’ Proc IEEE Globecom 1987, pp 1439-1443
STERN, J R., BALLANCE, J w., FAULKNER, D w., HORNUNG, s., and
PAYNE, D B : ‘Passive optical local networks for telephone applica-
tions and beyond‘, Electron Lett., 1987,23, pp 1255-1257
PENDLETON-HUGHES, s., et al.: ‘Forty channel wavelength division multiplexing for short haul wideband communications networks’ Proc IOOC-ECOC, 1985, p 649
HALL, R D., and BETTS, R A : ‘The design of a local line single mode
optical fibre transmission system’, British Telecom Tech J , 1986,4
METHLEY, s G : ‘A high sensitivity optical receiver employing optical feedback’ To be published in SIRA Fibreoptics & Elec- tronics Conference, April 1988, London
ERDMANN, R., et al.: ‘Prism gratings for fibre optic multiplexing’,
Proc S P I E , 1983,417, pp 12-17
EXPERIMENTAL SET-UP FOR D Y N A M I C
EVALUATION OF OPTICAL PARAMETERS
OF LIQUID SAMPLES EXPOSED TO
M ICR OWAVE RADIATION
Indexing terms: Microwave radiation, Optical measurement,
Biomedical electronics
An experimental apparatus was designed to carry out simul-
taneous microwave irradiation and optical analysis of liquid
samples, making possible the detection of field-dependent
reversible effects This preliminary work on enzyme-substrate
solutions seems to point out the effectiveness of the
assembled system and strongly suggest a physicochemical
influence of the applied field
Introduction: In recent years several studies have been carried
out to investigate the influence of nonionising electromagnetic
radiation on biological systems.’ In many of these studies in
vitro biological samples were examined after the exposure to
the radiation: as a consequence, possible temporary effects (i.e
effects that rapidly fade away when the field is turned o Q ’ ~
were not detectable To study such effects, the analysis of the
sample should be carried out during the irradiation without
affecting the exposure conditions T o this end optical methods
are among the less perturbative ones, and they have been
p r ~ p o s e d ~ ’ In these above works microwaves were fed into a
spectrophotometer cuvette from the inside and the absorbed power was calorimetrically evaluated
In this letter an experimental set-up is described, especially designed for sample irradiation entirely in waveguide, and continuous optical monitoring The all-waveguide system allows the easiest and most reliable evaluation of the power absorbed by the sample together with the simultaneous dynamic evaluation of its optical density Some preliminary results are also reported, that demonstrate the effectiveness of the apparatus
Experimental s e t - u p : The apparatus assembled for our experi-
ments is schematically shown in Fig 1 The microwave signal (signal source Marconi 6058B, 8.2-12.4 G H z ) was amplified (TWT amplifier Varian VZM6991G3,40dB gain) and was fed into a conventional R 100 rectangular waveguide reflec- tometer for X-band (8.2-12.4 G H z ) operation, that allows the evaluation of the power incident ( P i ) on the sample and the reflected one (P,) A spectrophotometer glass cuvette (10 x 10 x 40mm outer dimensions), axially inserted in the middle of an R 84 waveguide section (28 x 12mm inner dimensions), was used to hold 4ml of liquid sample The axes
of both waveguide and cuvette were vertical A suitable tapered waveguide section enabled us to connect the R 84 waveguide section to the R 100 waveguide reflectometer The SWR on the amplifier output was held as low as 1.1 by means
of a suitable matching of the sample holder (triple stub tuner,
T in Fig 1) and a 3 d B attenuator ( H P X382A) The power transmitted beyond the sample was negligible (transmission