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Good cable management practices also ensure that the fiber networks of today will be ready for the higher-bandwidth applications of tomorrow.. New issues, such as signal attenuation or c

WHITE P

Fiber in Broadcast and

Production Facilities

Ten Things Every Professional Should Know

For years, television broadcasters have relied on coax cable to route video and audio control signals and RF around their facilities Coax has proven itself to be easy to work with and reliable However, as the television broadcast business evolves from a single analog channel to a digital world, the industry is re-evaluating the role of coax In its place, fiber-optic cable is emerging as a logical solution for next-generation television signal routing, where greater bandwidth is needed to accommodate HD signals and multicast SD channels

As these applications drive fiber into more networks every day, many broadcasters’ deployment strategies overlook one major consideration Good cable management practices are the key to an effective fiber network, allowing for flexibility, fluid change, easier network maintenance and configuration and, most importantly, growth When a broadcaster uses good cable management from the start in its fiber network , the network grows more quickly Good cable management practices also ensure that the fiber networks of today will be ready for the higher-bandwidth applications of tomorrow

This paper explores the top ten things you need to know about fiber; things you should understand when planning for an upgrade that includes fiber Topics covered in this paper are:

1 Key Fiber Cable Management Concepts 3

2 Making Connections 4

3 Singlemode versus Multimode 5

4 Angled versus Ultra Physical Contact Connectors 6

6 Field vs Factory Terminations 8

7 Splicing vs Field Connectors 9

10 Planning for Future Growth 12

Top Ten Things to Know

For years, broadcasters have relied on coax cable to route

video, audio and control signals and RF around their

facilities Coax has proven itself to be relatively easy to

work with and reliable

However, as the broadcast business evolves from a single

analog channel to a digital broadcast world, the

continued roll of coax cable is being re-evaluated In its

place, fiber optic cable is emerging as a logical solution

for next generation signal routing, where greater

bandwidth is needed to accommodate HD signals and

multicast SD channels

Unfortunately, the knowledge that broadcast engineers

have gained about working with coax cable isn’t

particularly transferable to using fiber New issues, such

as signal attenuation or complete loss from severe

bending, proper troughing, crush load tolerance, and

cable density and accessibility, must be considered when

managing a fiber optic network

Proper cable management practices make fiber networks

less susceptible to accidental damage, quicker to install,

less expensive to own and operate over the long haul

and easier to expand as needs grow

Key cable management concepts include:

• Bend radius: At turns in fiber runs, maintain a 1.5-inch

bend radius Tighter bends may cause micro-bending

of individual fibers that allow light to escape the signal

path, resulting in signal attenuation More severe

bends can break fiber strands completely, resulting in

signal loss

• Cable troughing: Used to route fiber optic cable,

troughing systems provide a protected pathway for

fiber to traverse spans between rooms and equipment

racks Good troughing systems will keep fiber separate

from coax cable, protect it from out-of-tolerance

bends and promote neat, easily accessible runs

• Vertical cable protection: Allowing fiber to hang

unprotected from the back of equipment can be a

recipe for disaster Exposed cables are easy to snag

accidentally with a hand or foot, which can result in

damage to the connector or fiber itself Additionally,

over time the weight of hanging fiber can cause

bends outside the acceptable limit and consequential

damage to the fiber Proper vertical cable

management in panels or equipment bays provides

adequate support, cable protection and a transition

from the vertical run to the back of the equipment

that does not damage the fiber

• Cable pile-up: In horizontal fiber runs, it is unacceptable to allow a pile of fiber cable to exceed two inches Beyond that point, the weight of the bundle will surpass the crush tolerance limit of the fiber at the bottom of the stack, resulting in microscopic damage and signal attenuation

• Cable segregation: Keep fiber runs separate from legacy coax cable Coax is relatively heavy and can crush fiber cables Additionally, segregating coax from fiber ensures that technicians repairing coax do not accidentally damage the fiber cable while working on the copper

• Labeling: Develop good labeling practices Know where fibers originate and terminate Doing so will reduce maintenance time and the likelihood that a maintenance tech will make hasty decisions on fiber routing that can lead to a rat’s nest of cable and patch cords

• Density: When selecting products for a fiber network, remember future maintenance The more densely connectors are packed onto a panel, the more difficult

it will be for even the most dexterous technicians to maintain Remember, inevitably cables will be moved,

so the ability to trace and re-route them is critical to working efficiently

• Future proofing: When planning rack configurations with a given number of terminations to accommodate

a relatively low number of fibers for today’s requirements, don’t forget the future A fiber path that easily supports 12 fibers today may be inadequate

to support the 200 fibers needed in a few years Planning up front for the future can save the expense

of ripping out outgrown capacity down the road Proper cable management is extremely important to the successful conversion of broadcasters from coax to fiber The fact that a single fiber may transmit mission-critical signals, such as revenue-generating commercials and programming, underlies the importance of taking the steps necessary to manage fiber’s installation and use

Point at Which Light is Lost From Fiber Optical Fiber

Light Pulse

Macrobend

Area

in Which Light is Lost From Fiber

Optical Fiber Light Pulse

Radius of Curvature

1) Key Fiber Cable Management Concepts

Microbend

Integrating fiber into a broadcast facility requires a logical

means of connecting various devices throughout the

facility for production, playback and post-production

tasks, not unlike what has been done for years with coax

cable, patch panels and routing switchers

On the most basic level, there are three approaches to

network architecture:

• Direct connect: This approach is straightforward, but

exceedingly limited The output of one device is

connected to the input of another While the least

costly of the three, it is inflexible and requires

manually moving cables at potentially far-flung source

and destination points in order for them to be

reconfigured This approach has limited usefulness in

broadcast applications

• Interconnect: This architecture relies on a passive

patch panel to act as an intermediate point where

fiber from devices like tape machines and still stores

can be connected While eliminating the need to hike

to remote equipment locations to remove a cable from

one device so that it can be reconnected to another,

the interconnect architecture isn’t without its

downside The lack of circuit access makes remote

monitoring, testing and patching impossible

• Cross-connect: With a centralized cross-connect

patching system, achieving the dual requirements of

lower costs and highly reliable service is possible In

this simplified architecture, all network elements have

permanent equipment cable connections that are

terminated once and never handled again

Technicians isolate elements, connect new elements,

route around problems, and perform maintenance and

other functions using semi-permanent patch cord

connections on the front of a cross-connect system Here

are a few key advantages provided by a well-designed

cross-connect system:

• Lower operating costs: Compared to the other approaches, cross-connect greatly reduces the time it takes for adding cards, moving circuits, upgrading software, and performing maintenance Because all changes are made at one convenient location, technicians are able to quickly and accurately perform their work

• Improved reliability and availability: Permanent connections protect equipment cables from daily activity that can damage them Moves, adds, and changes are effected on the patching field instead of

on the backplanes of sensitive routing and switching equipment, enabling changes in the network without disrupting service With the ability to isolate network segments for troubleshooting and reroute circuits through simple patching, technicians can perform maintenance without service downtime during regular hours instead of during night or weekend shifts These three approaches to fiber network design and signal routing offer an ascending ladder of flexibility, convenience and control On the bottom rung is direct connection between devices For broadcast applications, this configuration is not recommended The interconnect architecture is most practical approach when there is limited rerouting of inputs and outputs and circuit access

is not important The cross-connect architecture stands

at the top of the ladder, providing the flexibility and reliability broadcasters need in signal routing

2) Making Connections: Direct, Interconnect and Cross-Connect Approaches

Direct Connect

Cross-Connect

Interconnect

As the broadcast industry makes its transition from

analog service to Digital TV, broadcasters are being asked

to address issues they hadn’t considered even a few years

ago What’s the right mix of multicast DTV channels?

Should HD programming be originated locally or should

SD be upconverted? What sort of DTV transmission

scheme is appropriate? Will distributed transmission solve

coverage problems and if so, how will STLs to multiple

digital transmitter sites best be accomplished?

With each new question comes a growing recognition

that the existing plant must be upgraded or in extreme

cases replaced entirely to answer the demands of

broadcasting in a digital world

As broadcast engineers grapple with these questions, the

need has never been greater to route more signals

between more devices with greater bandwidth Whether

it’s HD studio cameras, multiple STL links or distribution

of wide band signals throughout the station, fiber optic

cable offers an affordable alternative to copper coax

cable Additionally, its greater bandwidth capacity

future-proofs installations as increased bandwidth demands are

more easily accommodated than with copper

Fiber optic cable comes in two varieties: singlemode and

multimode Both have applications for broadcasters

Singlemode fiber optic cables transmit a single ray of

light used to carry modulated signals It is normally used

in applications requiring the transmission of signals over

a long distance In the broadcast industry, singlemode

fiber is well-suited for applications such as

studio-to-transmitter links, camera control units and runs from a

studio to satellite earth stations or to cable headends, or

between separate facilities on a broadcast campus

Multimode fiber optic cable carries multiple light rays

with different reflection angles within the fiber core

With a fiber core that’s thicker than singlemode fiber,

multimode cable is better suited for short runs, such as those between equipment and panels in broadcast facilities Multimode may be used to feed routers, servers, editing stations and video servers

Replacing copper with fiber is no longer economically impractical at broadcast facilities Once regarded as expensive, the proliferation of fiber for business LANs and WANs and its use in telecommunications

networks has brought an economy of scale to bear for fiber cable, connectors and components that can benefit broadcasters

A recent study comparing the costs of first-time installations of fiber with copper (CAT5, CAT5e and CAT6) found that an “all-fiber solution offered a lower total initial cost than the UTP-fiber network” for 12 scenarios that were studied

According to the study, conducted by Pearson Technologies Inc and the Fiber Optics LAN Section of the Telecommunications Industry Association, “In many cases deploying multimode fiber cable throughout the network

is significantly less expensive than installing new grades

of UTP copper cable.”

These new marketplace realities could not have been timed any better for broadcasters grappling with how to modernize their facilities for the demands of DTV in a cost-effective way

Fiber offers other benefits broadcasters will find attractive On a physical level, it requires far less space than coax Fiber connectors are also physically smaller than their coax counterparts

Additionally, fiber optic cable offers broadcasters a level of security that exceeds copper or microwave transmission because it is difficult to tap without breaking

3) Singlemode versus Multimode Fiber

Fiber Applications in a

Broadcast Family

Attaching a connector to a fiber optic cable will cause

some of the light traversing that fiber to be lost

Regardless of whether the connector was installed in the

factory or the field, its presence will be responsible for

some light being reflected back towards its source, the

laser Commonly known as return loss (RL), these

reflections can damage the laser and degrade the

performance of the signal The degree of signal

degradation caused by RL depends on the specs of the

laser; some lasers are more sensitive to RL than others

Different types of applications tolerate different degrees

of RL too The experience of the cable television

industry has shown video equipment only tolerates a

minimal level of optical return loss Similarly, high

bandwidth broadcast applications (such as

uncompressed HD) and long haul links between studios

and transmitter sites require minimal RL

The amount of optical return loss generated is related

to the type of polish that is used on the connector

The “angled physical contact” (APC) connector is best

for high bandwidth applications and long haul links

since it offers the lowest return loss characteristics of

connectors currently available In an APC connector,

the endface of a termination is polished precisely at an

8-degree angle to the fiber cladding so that most RL is

reflected into the cladding where it cannot interfere

with the transmitted signal or damage the laser source

As a result, APC connectors offer a superior RL performance of -65 dB For nearly every application, APC connectors offer the optical return loss performance that broadcasters require to maintain optimum signal integrity However, it is extremely difficult to field terminate an angled physical contact connector at 8 degrees with any consistent level of success Therefore, if an APC

connector is damaged in the field it should be replaced with a factory terminated APC connector

The “ultra physical contact” (UPC) connector—while not offering the superior optical return loss performance of

an APC connector—has RL characteristics that are acceptable for intraplant serial digital video or data transmissions When using UPC connectors, make sure your laser’s specs can handle the return loss your UPC connectors will generate

Offering –57 dB RL, ultra physical contact connectors rely

on machine polishing to deliver their low optical return loss characteristics Ultra physical contact polishing refers

to the radius of the endface polishing administered to the ferrule, the precision tube used to hold a fiber in place for alignment The rounded finish created during the polishing process allows fibers to touch on a high point near the fiber core where light travels Unlike APC connectors, UPC connectors can, with the proper tools and training, be repaired in the field

Fiber Casing

Fiber Core 8° Angled Endface

Ø2

Ø1

Ø3

Ø 3 > Critical angle defined by Snells Law

Ø 1 =Ø 2

Light is reflected into cladding along Ø 3

n1

n2

Fiber Casing

Fiber Core

polishing creates

a rounded finish

4) Ultra Physical Contact Connectors and Angled Physical Contact Connectors

Angled Physical Contact (APC)

Ultra Physical Contact (UPC)

Several fiber connector styles are popular today, including

SC, ST®, FC, Duplex SC, LC, LX.5®, MTRJ, and MTP, but

some are more appropriate for use at broadcast facilities

than others Of the traditional singlemode and

multimode connectors, FC, SC, LC, and LX.5 are the only

ones that can be “angled physical contact” (APC)

polished FC, SC, LC, LX.5 and ST can be polished using

the “ultra physical contact” (UPC) method

Newer, small-form-factor connectors, such as the LC

and LX.5, also are appropriate for broadcast

applications requiring density on patch panels

As discussed previously, in an APC polished connector

the endface of a termination is factory-cut precisely at

an 8-degree angle to the fiber cladding This design

reflects most of the return loss (RL) to the cladding, not

all back to the source As a result, APC is ideal for

high-bandwidth and long distance broadcast applications In

an ultra physical contact connector, machine polishing

creates a rounded finish to the fibers being connected

so that they touch on their high points While the RL

specs for UPC are not as good as APC, they are fine for

serial digital video and intraplant optical transmissions

The types of fiber connectors appropriate for broadcast

applications include:

• SC – “Sam Charlie” or “Snap Click”: The most

popular of all connectors, the SC style offers

excellent loss characteristics and comes in a

standard footprint It is easy to snap in and remove

The SC is pull-proof and is available in UPC and

APC styles

• FC – “Frank Charlie”: One of the most popular

connector styles, the FC offers excellent loss

characteristics and comes in a standard footprint

The FC inserts by twisting a threaded connection

with key alignment It is pull-proof, being difficult to

remove Made from metal components it is available

in UPC and APC styles

• ST ® – “Sam Tom”: Very similar in appearance to a

BNC connector, the ST is a screw-on type connector

It does not offer the pull-proof resiliency of SC and

FC connectors ST connectors, which are made of

metal components, are only available with UPC

polishing In recent years, the popularity of ST

connectors has waned as the use of SC and FC

connectors has grown

• Duplex SC: Offers the same features as the SC style

but supports two-way communication

• LX.5 ® : Exactly half the size of an SC connector, the

LX.5 offers twice the density of its larger counterpart Key to the LX.5 is its use of safety shutters on both the connector and the adapter body to provide protection from dust, dirt and damage from ferrule endface handling Available in UPC and APC

• LC: The LC comes in a small-form-factor that

competes with the LX.5 The LC features are similar

to SC, but its size allows double the density

Available in UPC and APC

When designing a fiber network for routing signals through a broadcast facility, standardizing on a single connector type will make network repairs and technician training faster and less expensive However, despite efforts to standardize on a single connector style, it may be necessary to use a hybrid cable to move the set standard

Adopting the LC or LX.5 style connector makes sense in

a broadcast facility because of the sheer number of sources and destinations common at stations and the use

of multicore fiber to route signals between them The smaller size of the LC and the LX.5 connector means more individual strands of multicore fiber can be broken out, connectorized and accommodated on a patch panel

As long as the panel is designed ergonomically so that technicians and engineers can actually grasp a patch cord connector connected to a densely-packed panel, this application of LC and LX.5 connectors is sound If the panel is packed too densely, there is always the option of breaking out individual fibers of a multicore run to larger, easier-to-grasp SC connectors

Ease of use and protection against fibers being accidentally pulled is more important in broadcast facilities, as fiber panels are typically installed in high-traffic areas

6) Connector Styles

Broadcast engineers who cut their technical teeth

attaching connectors to coax cable might be surprised

to learn that when working with fiber, relying on

factory-terminated cables offers several advantages over

field termination, including performance and savings in

labor, material costs and installation time

Unlike field-terminated fiber, preconnectorized cable

assemblies are guaranteed to work out of the box to

the highest performance specification Under the best

circumstances, field-terminated cables offer 0.5 to 0.25

dB signal loss, while factory-terminated fiber delivers

typical loss of less than 0.2 dB Factory termination will

provide consistent loss values, making network

planning more accurate

Engineers who have worked hard over the past several

years to implement video production workflow

solutions that improve productivity have personal

knowledge of the ongoing efforts at stations to work as

efficiently as possible and to use labor wisely Against

this backdrop, using factory-terminated fiber in stations

makes a lot of sense

The labor savings associated with using

factory-terminated cables in most instances make it a more

economical solution than field termination of fiber

cables Not only do factory-terminated cables eliminate

the labor costs associated with installing connectors in

the field, they also do away with the need to spend

money on re-doing work that has failed as well as the

cost of additional connectors Factory-terminated cable

comes from the manufacturer where it was prepared

under the supervision of fiber optic experts in an

environmentally controlled setting with quality

inspection and testing Connectors are attached to

individual strands of fiber in an automated factory

process that is not as subject to human error Once

attached to the fiber cable, the connections are tested

to ensure quality and performance

When fiber is terminated in the field, bulk cable arrives

at the broadcast facility on optical cable reels with packages of connectors That cable must be pulled between points and attached to patch panels at both ends of each run Before it can be attached to the panel, technicians must attach connectors to each strand of fiber Those field-terminated connectors, which get plugged into the back of patch panels, can fail or perform below acceptable signal loss tolerances Relying on factory-terminated cable requires some forethought and planning Knowing where panels must

be located and the length of runs from the panel to various pieces of equipment is necessary, but it’s also important to know how best to bring panel, fiber and equipment together One approach is using multifiber cable with factory-terminated connectors attached to one end for the equipment side of the run At the patch panel, a factory-connectorized pigtail plugs into the back of the panel leaving a factory-prepared stub end ready for splicing Station technicians then splice individual strands of the multifiber cable to single strands of fiber making up the pigtail

The other approach is similar Here factory-connectorized pigtails are used on both the equipment and the patch panel ends of the run Broadcast technicians then splice individual strands of fiber (see the next section on splicing to learn more) in the multifiber cable between both ends to individual fibers in both pigtails

For broadcast engineers who have grown up in the business cutting coax to length and attaching connectors, these approaches might seem a little foreign However, the clear advantages of lower labor costs, higher performance and the elimination of wasted material and time offered by using factory-terminated fiber optic cable make a little re-orientation in engineering mindset and practice more than worthwhile 6) Field versus Factory Connector Termination

Common practice among broadcast engineers calls for

cutting coax to the desired length and attaching

connectors in the field Doing so with coax is fast, easy,

and results in precise control over cable length

However, that isn’t always the best solution for fiber,

especially when cable runs are longer than 25 meters,

singlemode fiber is being used, or a degree of

permanency is required

For those situations, splicing individual fibers as shown

in figure 1 offers an attractive alternative Among the

benefits of splicing fiber are lower signal loss, more

predictable results and the faster speed at which it can

be done by a trained technician

Fusion splicing of fiber in the field offers substantially

greater efficiencies in time and performance than

attaching connectors Fusion splicing fibers is done by the

following process:

• Outer jacket removed from multicore cables and

broken out to individual 900 micron cables and

strength member or yarn trimmed

• Individual fibers are stripped to 250 micron bare fiber

• Fiber cleaved, resulting in a flush end

• Fiber prepared for splicing by cleaning the ends and

putting a shrink tube over one end

• Both cables put into the alignment device on the

splicing equipment, which will align the fiber ends

• Laser fusion procedure initiated on the equipment

• Technician removes the fusion splice and visually

inspects the junction with a high powered microscope

(typically part of the splicing equipment kit)

• Fusion splice secured into the splice holder on the

fiber panel splice tray

Trained technicians can splice two strands of fiber together in as little as 5 minutes, which compares to 15 minutes per field-terminated connector The efficiency of splicing becomes even more pronounced when

comparing splicing a 24 fiber cable to field terminating it – 2 hours vs 12 hours

The difficulty of adding connectors in the field also means that the yield of acceptable connections will be directly related to the skill level and experience of the technician Unlike fusion splicing, there is no automatic labor savings associated with field terminating connectors and testing connections Anecdotal experience indicates that as many as 50 percent of field-installed connectors fail when done by green technicians, resulting in time-consuming, costly do-overs

In terms of performance, field-terminated singlemode connectors can leave engineers wanting Under the best circumstances, they offer 0.25 dB signal loss, while loss from fusion splicing typically is 0.01 dB

Splicing is most appropriate for long runs of fiber between buildings or separate floors of the same building and is best-suited for applications where connections are intended to be permanent It provides the best solution for connecting points separated by an unknown distance

Conversely, preterminated connectors or field termination, as shown in figure 2, is a better solution for short runs of multimode fiber Field-terminated

connectors make the most sense for multimode fiber between two points separated by a known distance 7) Splicing vs Field Connectorization

Figure 1: Splicing at both

panels is most appropriate

for long runs of

singlemode fiber where

distances are unknown

and connections are

intended to be permanent.

Figure 2: Field terminated connectors

are a good solution for short runs of

multimode fiber between points

seperated by a known distance.

Unmanaged patch cord slack is a silent threat to

mission-critical operations at broadcast facilities using fiber optic

cable to route signals around the facility A misplaced

foot or wandering hand can accidentally snag exposed

loops of fiber patch cord and pull it with enough force to

damage optical fibers and harm connectors More

importantly, untended patch cord slack that gets yanked

might be carrying a commercial to air, requiring

expensive make-goods, or interrupt an edit session for an

important client In either case, the resulting harm could

be far greater than cost of a little prevention

Broadcast engineers planning an upgrade or system

change-over to fiber optic cable should include storage

of slack patch cords in their plans from the outset

Besides the ability of proper slack management to tidy

up the look of a facility, it also elevates the confidence

level of station engineers as they work in equipment

racks free from the fear that a false move might

accidentally do harm

Another important benefit of having a dedicated slack storage system for patch cords is the ability to specify a single patch cord length for the entire plant Proper slack storage means that a 5-meter patch cord can be used for

a long or short patch without fear that dangling excess fiber will be damaged

Stations entwined in a rat’s nest of patch cords can improve the appearance of their rack areas and make patching much simpler with proper slack storage

Systems that store patch cord slack properly maintain a minimum bend radius of 1.5 inches to protect against damage to fiber They also provide easy access for convenience when it’s necessary to reconfigure a patch From integral storage compartments in stand-alone termination cabinets to 19-inch 1RU fiber management trays, slack storage systems can take many shapes But the common thread among all of these systems is that extra patch cord lengths are neatly stored, protected from damage and aren’t exposed to accidents that can negatively impact the ability of a facility to earn revenue 8) Slack Storage: Protecting and Managing Fiber Cables