Tài liệu It''''s Happening in the Hub pdf

Key innovations include: • Miniaturized splitter modules with plug-in installation that allow easy additions and upgrades • High-density termination fields with connectorized harnesses

It's Happening in the Hub

It’s Happening in the Hub

Fiber Distribution Hubs (FDH) continue to play a vital role in supporting rapid deployment and connection in FTTP networks Innovation in FDH design occurs

at a rapid rate and next generation features appear in newer FDH enclosures Key innovations include:

• Miniaturized splitter modules with plug-in installation that allow easy additions and upgrades

• High-density termination fields with connectorized harnesses allowing modular growth and flexible rearrangement

• A wide range of sizes and mounting configurations that retain craft-friendly fiber management and maintenance features

• Highest performance optical connectors and splitters available; all the optical components and enclosures have completed a rigorous regiment

of independent testing far beyond any test program seen in the industry

to date

As a result, FDH products have been widely accepted in FTTP networks FTTP

is now seeing large-scale deployment and FTTP deployment is definitely still happening at the hub

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After years of research and experimentation with

access networks, many network providers have settled

on Passive Optical Network (PON) architectures as

the direction for future subscriber access The PON

architecture has been adopted as a standard in

ITU-T G.98.x that defines the protocols, data rates and

operating wavelengths necessary to support network

services At the same time, the standards have

established power budgets and parameters for the fiber

optic plant to ensure reliable transport all the way to the

home The technology of high-speed PON equipment,

combined with broadband fiber offers the potential for

connecting high bandwidth services directly to the home

The standards ensure interoperability of equipment

and therefore have driven down the cost of deploying

all optical networks When adding in the cost savings

associated with operating an all-passive optical plant,

PON networks are attractive for overbuild as well as new

network construction

The initiative to build PON networks is often referred to

as Fiber-To-The-Premises (FTTP), to emphasize the vision

of connecting fiber from the central office/headend

(CO/HE) all the way to the premises A typical FTTP PON

distribution network is depicted below PON architecture

includes Optical Line Terminal (OLT) equipment at

the CO/HE that bundles voice and data services OLT

equipment utilizes wavelength division multiplexing

(WDM) technology to provide bidirectional voice and

data services (110nm/1490nm) over a single fiber

Additional WDM components at the CO/HE allow

integration of video services onto the same fiber at the

1550nm wavelength

OLT equipment ports are connected through optical splitters, thus allowing a single port to serve multiple subscribers The split ratio in PON networks can vary, but typically networks are planned with 2- or 16-way splits The architecture may be configured by concatenating the splitters at a single point Most networks are planned with 1x2 splitters centrally located for easy access for additions, service and maintenance

PON architecture includes Optical Network Terminal (ONT) equipment at the premises for resolution of voice, data and video services Standardization of ONT equipment allows the same equipment to provide services for Fiber-To-The-Home (FTTH), Fiber-To-The-Business (FTTB) and Fiber-to-Multiple-Dwelling Units (MDU) applications Combining these applications into the FTTP network architecture provides economies of scale for construction and service deployment

The Optical Distribution Network provides physical connection between the CO/HE and the premises and includes various cabling segments including feeder, distribution and drop These various segments are typically joined together by connectors and splices The Fiber Distribution Hub (FDH) is one of the key elements located between the feeder and distribution segments and contains optical connectors and splitters to provide easy access and flexibility The advantage of configuring the network with connectors is to allow flexibility for service provisioning and for network testing

It's Happening in the Hub

Fiber-to-the-Business ONT

FDH CO/HE

OLT Optical Distribution Network

Fiber-to-the-Home

Fiber-to-the Multi-Dwelling Unit

Network Architectures

The Fiber Distribution Hub is a key interface between

feeder cables extending from the central office to

distribution fibers routed to subscribers The FDH

serves an analogous function to serving area cabinets

(SAC) used in copper-based networks to interconnect

the feeder and distribution segments of the network

The hub becomes a primary point of flexibility in the

network to connect subscriber circuits As service is

required, technicians access the FDH enclosure to route

connections to complete subscriber circuits The FDH also

serves as a central location for fiber optic splitters This

is where the PON network differs significantly from a

copper network

The optical splitters allow the PON OLT port to be

shared among multiple subscribers via the 1xn split, thus

defraying the cost of the OLT By locating the splitters in

the outside plant close to the serving area, the cost of

feeder fiber is also significantly reduced For instance,

when a 1x2 splitter is placed in the FDH, one feeder

fiber may be routed into a neighborhood and provide

service connection to 2 subscribers Another reason to

locate splitters in the FDH is that splitters can be deferred

until they are needed to satisfy service requirements The

FDH can be accessed to add splitters as service demands

grow Newer hub designs accept modular splitters

that quickly plug into the FDH to allow capacity to be

expanded within a few minutes

Typically, the FDH is equipped with one stub cable that

is spliced into a feeder cable and another stub cable that is spliced to a distribution cable Construction is usually completed using standard splicing techniques (usually mass splicing) with splices stored in standard splice closures

Key FDH Capabilities – and Innovations

The FDH enclosure provides a crucial craft interface in the outside plant environment Therefore each major function of the hub supports easy craft access for service and maintenance

FDH Pad and Pole

Central Office/Headend

Underground Distribution

Aerial Distribution

Fiber Management Parking Adapter

Termination Splice Shelf and Trays

Splitter Shelf and Modules

FDH Network Function

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Termination Field

The termination field provides a location for terminating

fiber distribution cable on optical connectors and

adapters The termination field is sized to support the

number of subscribers located in the distribution serving

area downstream from the FDH FDH enclosures support

a range of termination field sizes (144-, 216-, 42-, 576-,

816- or 1152-terminations)

The termination field provides easy access to both sides

of the adapter to facilitate cleaning and maintenance

ADC FDH enclosures feature a unique swing frame

design, a hinged chassis containing all the key optical

components including splitters, connectors and splices

The design allows easy access to optical components

from the front and rear for cleaning and troubleshooting

and is especially valuable in installations where access is

limited to the front of the cabinet only, for example in

pole mounted applications Large cabinets deployed in

ground mount applications feature doors on the front

and rear to allow full access to connectors and splitters

from the front and back

Terminations in the field are clearly marked to provide

accurate identification of each subscriber termination

The termination field provides organization and

protection for fiber jumper connections as they transition

into the fiber management section of the enclosure

Recent FDH innovations include high-density

component packaging resulting in significant reduction

of enclosure sizes High-density termination fields with

connectorized harnesses allow modular growth and

flexible arrangements

High-Density Termination

Early FDH termination requirements were often matched

exactly to the requirements for subtending living units

in the immediate fiber serving area For instance, a 216

fiber hub was specified to support a fiber serving area

of approximately 200 subscribers, providing a small

(approximately five to ten percent) portion of spare

fibers routed into the serving neighborhoods With more

experience, planners realized that additional fiber capacity

downstream could be required for unforeseen changes

in the network or in services supplied However, while

specifying increased numbers of spare fibers, resulting

in increased fiber termination requirements, users were

reluctant to increase the overall size of the enclosures

Therefore, fiber termination fields had to handle the

increased capacity within already defined enclosure

sizes This involved increasing termination density and

also increasing the fiber handling capacity for a particular

enclosure For example, enclosures previously handling 216

fibers were upgraded to terminate 288 fibers This increase

in density provides the desired fiber counts along with the

spare growth capacity required for typical fiber serving

areas, while maintaining the overall size of the enclosure

Modular, Scalable Distribution

In overbuild scenarios, the termination field on the distribution side is fully populated with connectors at the initial installation and the enclosure is provided with fully-terminated stub cables sized for the enclosure’s direct termination needs Network planners, however, considering newer greenfield developments, look for ways to defer cost and match the FTTP build to the pace of the development’s build A new development, constructed in phases over a period of years, may not initially require an FDH with a fully-populated termination field This situation may be better served

by gradually deploying terminations as needed To satisfy this requirement, the FDH enclosure includes modular blocks that allow terminations to be added as required Termination blocks can easily be spliced into the enclosure or the enclosure can be connectorized with multifiber connectors (MFC) to provide quick connection

to termination blocks as they are installed The modular termination block allows upgrades to the FDH to match the requirements of the FTTP network deployment, thus deferring hardware costs

Improved Overall Performance

Advances in planar splitter technology have dramatically decreased the amount of signal loss when a single fiber

is split into several outputs Innovation in component performance has resulted in lower loss connections, in both the termination fields and the splitters Improved connector performance for both the widely used SC,

as well as MFC connectors proposed for modular components, allows connectorization to replace splicing on both feeder and distribution fibers while still meeting the overall loss limits within the FDH Using connectorization for input fibers and distribution panels greatly reduces the amount of time required to install and upgrade an FDH

It's Happening in the Hub

Splitter Field

Splitter modules are designed to snap-in to the splitter

field and can be added as required by service demands

The splitter field protects, organizes and routes both

the input and output fibers The optical splitter modules

provide up to 2 connectorized pigtail outputs and one

pigtail input

Early generations of FDH were deployed fully loaded with

splitter modules that featured storage ports, sometimes

referred to as parking lots, located on the front of the

module to stage splitter output pigtails temporarily until

they were connected into service The splitter module

assembly included modular “parking adapters,” each

holding 16 or 2 connectors As a splitter module was

installed, the fibers were fed into the fiber management

trough and the parking adapters were snapped into place

in the parking area Individual connectors were then

easily separated from the parking adapter and routed to

the termination field during service turn-up

Recently, the parking lots have been relocated to a spot

in the FDH away from the splitter modules The parking

adapters are removed from the splitter module, allowing

the splitter module to be reduced in size One design

includes hinged parking that allows 50 percent reduction

in splitter module size, and hence FDH enclosures that

are 50 percent smaller

Today, most carriers take an incremental approach to

adding splitter modules – deploying FDH enclosures

initially with just the splitter modules required to begin

service connections This reduces the number of parking

lots required for pigtail outputs In essence, splitter

outputs “time share” parking lots; as the outputs of the

initial splitter modules are placed into service, the parking

lots associated with those outputs become available for

parking subsequent splitter module outputs This allows

a significant reduction in the size of the parking lot, and

consequently, a reduction in the size of the FDH

New miniaturized splitter modules feature planar optical splitters and are 75 percent smaller, another contributing factor in the reduction of the FDH’s size Additionally, innovation has improved the way splitter modules are installed into the enclosure First generation modules were designed with the splitter module input extended

as a pigtail, which was spliced to feeder fibers As each subsequent splitter was installed, it was spliced to feeder fibers staged in splice trays Splicing consumes valuable time, and adds costs to service turn-up Earlier improvements included connectors on the feeder fibers that allow quick connection during splitter module installation; a connector on the pigtailed input and a connector on the feeder fibers mated at a connector panel in the enclosure This approach provides a simple, much improved method for quickly installing splitters Connectorization of the feeder fibers at the FDH also allows testing on the feeder from the FDH if required However, connectorization of the feeder fiber also raised a safety concern regarding high power when analog video is transmitted over the path To address this concern, connectors can be angled or adapters with shutters provided to prevent a technician from accidentally looking into the high-powered termination Further innovations have resulted in a backplane connector system for installing splitter modules In this configuration, feeder fibers are terminated with a standard connector pre-positioned on the backplane to receive a plug-in splitter module with a mating connector The backplane connector is shuttered for safety so that

a technician cannot accidentally look into an unmated splitter module As a splitter module is inserted into the backplane receptacle, the module presses open the shutter to allow the splitter module connector to mate with the backplane connector This “blind-mate” approach using a common backplane technology improves efficiency in future expansion activities

It's Happening in the Hub

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Splice Area

The FDH features a splice area to connect feeder fibers

or other cables routed into the enclosure One use for

this area is the splicing of additional splitter modules

to feeder fibers as the modules are added to the FDH

enclosure An alternative to splicing the input is to

include a connector at this location

Factory Pretermination

FDH enclosures typically include two preterminated stub

cables One stub cable is pre-connected to the optical

splitter module input so that it can be field-spliced to the

feeder cable The other stub cable is pre-connected to

the termination field, so that it can be field-spliced to the

distribution cable These cables attach to the enclosure

using standard grip clamps and liquid-tight compression

fittings seal the cables at the enclosure entrance

Orientation of the enclosure stub cables varies, depending

on the FDH’s mounting method

Craft-Friendly Fiber Management

The FDH provides total fiber management using a

unique front facing cross-connect design The front fiber

management allows splitter module outputs to be routed

and staged within the enclosure for efficient connection

into service at a later date

Vertical channels using storage loops manage excess fiber

slack The entire cabinet can be interconnected without

congestion Connectorized pigtail ends are stored on

bulkhead adapters on the front of the module so that

connector ends can be identified quickly and connected

into service Fiber strain relief and radius control is

provided through the enclosure

Indoor Configurations

As FTTH moves into densely populated areas, the use

of indoor fiber distribution hubs becomes popular due

to the number of units within a particular building, as

well as space restrictions outside the buildings Indoor

FDHs provide all the same features as an outdoor FDH,

but are typically smaller and lighter They do not need

to meet the same harsh environmental requirements as

the outdoor FDHs Fiber count capacity ranges from 72

fibers to 42 fibers, accommodating small to large

high-density buildings

Below-Grade Configurations

Another option for high-density areas, as well as areas that do not allow above ground enclosures for zoning reasons, are below-grade Fiber Distribution Hubs These compact enclosures are stored in below-grade vaults when not being accessed for service configurations

Qualification

A complete FDH qualification program draws from a wide array of existing standardized tests with existing procedures In some cases, new test procedures have been developed and refined to support the new configurations and new technologies The overall program is composed primarily of testing regiments drawn from Telcordia Generic Requirements First and foremost, the qualification program involves testing optical connectors to GR-26-CORE, Issue  All connectors utilized in the FDH enclosure are subject to the complete outdoor service life requirements and to the full spectrum of long-term reliability tests In addition to testing at 110nm and 1550nm as required in GR-26, the test programs included additional test wavelengths of 1490nm and 1625nm to assure users that all operating wavelengths and all potential maintenance channels would function under the harshest conditions

Optical splitters are fully tested to ensure trouble free performance over the life of the network The splitters use planar technology and follow a qualification program aligned with service life testing in GR-1209-CORE and long-term reliability testing in GR-1221-CORE Because

of the nature of testing very large devices (1x2 ports), special sampling techniques were developed for optical measurement characteristics such as directivity Splitter qualification is conducted at the full operation spectrum

of four wavelengths including 110, 1490, 1550 and 1625nm All testing is done in the format of the optical module that plugs into the FDH enclosure, representing the exact configuration deployed in the field Tests for the new enclosures include a full range of environmental and mechanical tests Optical characterization is conducted

at the same four wavelengths as the connectors and splitters Additionally, several of the tests such as thermal cycling and seismic qualification are optically monitored during the test at 1625nm, which represents the worst-case scenario from a fiber integrity perspective

Independent testing of the qualification program demonstrated the FDH’s reliability, assuring a performance level and longevity expected in an FTTP network

Successful testing of all aspects of the enclosures, including performance of optical connectors and splitters, have given users the evidence and confidence to support wide scale deployment of FDH enclosures in the access portion of FTTP networks

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ADC Telecommunications, Inc., P.O Box 1101, Minneapolis, Minnesota USA 55440-1101 Specifications published here are current as of the date of publication of this document Because we are continuously improving our products, ADC reserves the right to change specifications without prior notice At any time, you may verify product specifications by contacting our headquarters office in Minneapolis ADC Telecommunications, Inc views its patent portfolio as an important corporate asset and vigorously enforces its patents Products or features contained herein may be covered by one or more U.S or foreign patents An Equal Opportunity Employer