Portable Optical Time Domain Reflectometers (OTDRs) are now being merged with Optical Loss Test Sets (OLTS). They are smaller, lighter, easier to read, and capable of handling the sort of advanced testing being demanded by forthcoming standards. The new breed of OTDRs are also faster, capable of taking higher measurements, are more accurate, and able to provide precise distance measurement.
In short, OTDRs are continuing to evolve as manufacturers strive to make them attractive to contractors who have largely shunned them in the marketplace due to their hefty price tag. Both manufacturers and members of standards committees say installers may want to take a second look at this next generation of products. OTDRs will be needed, they say, as optical-fiber networks become more complex and demanding. New products will also offer many more capabilities.
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Some of the latest OTDR developments at a glance:
- Fluke Networks (www.flukenetworks.com) is unveiling an OTDR that is simple to use, and capable of both OLTS and OTDR troubleshooting while incorporation a video microscope for fiber end-face inspection. This latest solution, called OptiFiber, is designed for short-haul installations, such as those on campus and in-building networks.
- Noyes Fiber Systems (www.noyes-fiber.com) plans to make available a more portable, less costly model. It will soon unveil the M100, a multimode/singlemode OTDR that will weigh less than 3 pounds.
- Acterna Inc.'s (www.acterna.com) next model of the Media Test Set (MTSe) will combine an OTDR with spectral analysis, polarization mode dispersion, and chromatic dispersion functions.
- Anritsu Co. (www.anritsu.com).offers the MW9076 series claiming fast speed of measurement, easy user interfacing, and a clear display for indoor or outdoor use.
The OTDR is becoming more important as cabling architecture changes, and networks in industrial settings are intercepted with optical fiber. The portable devices are being used in the enterprise as well as outside plant space for troubleshooting and monitoring networks, and are typically marketed to contractors or private network owners.
Some of the changes in the next generation of OTDRs are being pushed by an evolution of standards, which are causing new ripples in testing requirements and consequent changes in test equipment.
A recent BICSI (www.bicsi.org) survey is also forcing OTDRs into the limelight. The Telecommunications Industry Association (www.tiaonline.org) recently worked with BICSI and distributed more than 10,000 surveys to designers, manufacturers and end users. Respondents were asked if they are confident that their present optical-fiber testing will support their applications. A surprisingly high percentage (40%) said "no."
The study has met with different interpretations. "I don't believe that contractors, in gereral, lack confidence in current test equipment or procedures," says Chris Blair, manager of new product development for the Noyes Fiber Systems division of AFL Telecommunications (www.noyes-fiber.com), based in Belmont, NH. Blair is also a member of the TIA's TSB-140 subcommittee. "If you look at that survey, a big percentage of the respondents say they want clarification."
And some manufacturers interpret the survey results as a voice calling for better, more thorough optical-fiber testing. OTDRs could play a big part in this testing, and manufacturers want their products to get out on the market.
"About 60% of the survey respondents said they were confident with their applications running after testing," says Bob Jensen, chairman of TIA TR-42 and of the TSB-140 task group. "Then we asked them if they want to have testing clarified, and 82% said they did. So, we can tell from the numbers alone that of those people who were confident, they still wanted clarification."
Hedging on high prices
A recent QuickVote report from the Cabling Installation & Maintenance Web site (www.cable-install.com) reveals that installers are showing a growing interest in OTDRs. Still, only a small percentage of those who responded to the online survey say they will definitely buy one.
The majority of those who responded to the QuickVote (34%) said they own an OTDR already. And while 31% of the respondents said they don't own one and don't plan to purchase one, 23% said they might purchase one in the future. Only 12%, however, said they don't own an OTDR and definitely plan to purchase one in the future.
Portable OTDRs are an ideal troubleshooting testing tool, but are not the easiest sell because their high price have made them a tool that contractors would like to have but can't necessarily afford.
"They are quite expensive, and unless you do a lot of fiber installation, you wouldn't have a need for one," says Gary Lemoine, project manager for Telcom Network MassMutual Financial Group, based in Springfield, MA.
"The OTDR has always been usable, but not always affordable," agrees Blair. He says smaller contracting firms are least likely to purchase OTDRs, and some contractors are afraid to ship the devices to a distant installation project, worried they could be damaged en route.
"Do most contractors want one? Yes," says Blair. "Can they usually afford one? No."
"If you can afford to buy an OTDR that costs $10,000, that would be OK," agrees Jerome Laserriere, product manager, MTS and OTDR, for Acterna Inc. , which has offices in Germantown, MD. "But I'm not sure that people would be able to do that except the contractors who are doing long distance or metropolitan testing."
Some manufactures are choosing to make less costly OTDR adapters to compete with more pricey, traditional OTDRs.
IDEAL Industries, Inc. (www.idealindustries.com) has made a less costly adapter that can be attached to its copper and optical-fiber testers. The TRACETEK adapter, which costs $3,000, can be attached to the LANTEK 6 and 7 testers and give them the same functions as an OTDR. Each of the testers are sold for around $6,000.
Ed Pivonka, representative from product marketing, says sales for the TRACETEK are taking off primarily because it represents an inexpensive alternative to many of the OTDRs now in the marketplace. "The market for OTDRs would be much greater if there was a more reasonably priced OTDR," he says.
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Manufacturers and distributors, meanwhile, describe the attempts to reduce the price of an OTDR as a double-edged sword. At a time when profit margins are being eroded in a slow economy, they say the prospects of cutting away at an OTDR's price is, to say the least, unattractive. Furthermore, manufacturers face a real challenge when it comes to reducing the costs of the complex devices.
That's the belief of Larry Wesson, president of Aurora Instruments Inc. (www.aurora-instruments.com), based in Philadelphia, PA. Aurora Instruments manufactures fusion splicers, and distributes the FiberPal OTDR. "These days, with the industry in the doldrums, there is not much of anything being bought," says Wesson. "I have seen a lot of price erosion, and it's not good for the manufacturers. They are being squeezed."
Still, many argue that, high price or not, OTDRs are definitely needed. And they will soon be needed more than ever before.
An OTDR measures loss over distance, and can be used in either singlemode or multimode networks. Part of the reason they are needed is that they are used to measure wavelengths, and fiber has not been tested for insertion loss at 1625 and 1480 nanometers (nm). These wavelengths are sensitive to cable bending, and it is important to take OTDR measurements during installation.
An OTDR is likewise useful for fiber link categorization, which should be completed when 10-Gigabit Ethernet systems are installed. It is also used to measure the loss and reflectivity of connections and splices. But many contractors admit they are unsure of when they should use an OTDR on the job. And indeed, no standard says they must use one today.
Testing per standards
A TIA subcommittee, TR-42.8, recently approved a project that clarifies the testing of optical-fiber cabling. The project is designed to take some of the confusion out of the optical-fiber testing procedure, and clarify when an OTDR should be used.
The written bulletin will include two tiers of testing that can be chosen by a designer to be specified in a project. Tier 1 testing will include link loss testing with an optical-loss test set (OLTS) and polarity verification by means of the OLTS or a visual fault locator. Tier 1 also includes lenght "verification," which can be performed using an OLTS, OTDR, or by inspecting design drawings or cable sheath markings. Tier 2 testing will include the parameters of Tier 1 and also an OTDR trace of the installed cable. Tier 2 testing involves seeking a baseline trace that shows loss over distance, and includes fault-location using an OTDR.
The two-tier testing method is being incorporated to give installers the most complete picture of fiber installation. It will also give network owners proof of a quality installation. Tier 2 testing is considered a useful test for diagnosing a problem and for quality control, but it is not required by the industry.
Tier 2 will be explained through TSB-40, an upcoming TIA clarification standard. One of the goals of TSB-40 is to clarify when a contractor should use an OTDR or OLTS. An OLTS uses a light source and a power meter, and lets an installer measure link attenuation. OLTSs are required by TIA/EIA 568-B, and can measure insertion loss more accurately than an OTDR.
Laserriere says, "There is a need to define some of the measurements." He also says the different tiers of testing are being mandated by ever-changing cabling architecture. Networks are being intercepted with optical fiber, particularly in industrial settings. Consequently, cable is being developed to support these high-speed applications.
"People are pushing the bandwidth closer and closer to the desk," agrees Eric Anderson, marketing manager for Fluke Networks, based in Everett, WA. "They are putting more fiber in their networks, and this is driving the need for faster networks to 10 Gigabit." One consequence of this, Anderson says, is that optical-fiber cabling loss budgets are being stressed. OTDRs, which are capable of showing losses that will affect these networks, can draw attention to such cable stress.
Today's OTDRs
Manufacturers say they are trying to meet these issues, and are also concentrating on reducing the size of OTDRs, making them easier to carry in the field while still featuring a display screen that is easy to read. They are likewise struggling to bring down the weighty pricetags, making OTDRs more attractive to the small contractor.
Fluke Networks' OptiFiber, which is designed to conduct loss testing for multimode fiber, combines a light source and power meter with an OTDR while including a video microscope to view any problems found at connections. The device offers a shorter dead zone than a typical OTDR. A dead zone refers to an OTDR's recovery time following a reflective event at the shortest pulse width.
The OptiFiber is a platform project upon which Fluke Networks plans to expand. There will eventually be six versions of the OptiFiber on the market. The multimode version will be available before this year ends, and the singlemode version is scheduled to be available in the first half of 2003.
Designed to simplify the analysis of events, OptiFiber has been engineered for completing Tier 2 testing and certification. In fact, Anderson describes the OptiFiber as the only integrated solution now on the market for TSB-140 certification. "Its features make it quick to troubleshoot problems," says Anderson.
The OptiFiber has a large, bright color display, designed to help an installer see two events that are as close as one meter apart rather than as a single event aiding in the dection of a bad connection. Its camera port has a fiber inspection camera plug-in. The OptiFiber can save the image taken by the camera, and has digital storage capabilities of 8 MB to 256 MB or higher. It weighs in at just under 5 pounds.
Price, however, is a challenge still being faced by Fluke Networks. The OptiFiber will cost about $15,000.
The price is right
Noyes Fiber Systems is aiming for OTDR models that address the price issue. This month, the company will unveil the M100, a multimode/singlemode OTDR. The lightweight, handheld device will have all of the basic features of an OTDR and will cost about $9,000.
The company's M600, a four-wavelength multimode/singlemode OTDR, costs under $15,000. The M600 can be used in a LAN environment, outside plant, or fiber-to-the-home installation, and has a range of up to 80 kilometers.
The M600, like all OTDRs, generates short pulses of light, samples reflected light as a function of time, and converts these samples into a graph or "trace" of insertion loss versus distance. Based on the shape of the trace, the M600 can locate and analyze fiber link events such as connections, splices, bends and breaks.
Traces can be saved to internal non-volatile memory using the M600's CompactFlash, a removable mass storage device. The device is capable of storing more than 1,500 traces, or floppy disks. By using the supplied CompactFlash reader or floppy disk, saved traces can be transferred to a PC for archiving, printing, and analyzing with the Trace600 Windows software.
Singlemode solution
Acterna is working in the singlemode market with its MTS100 OTDR, and Laserriere says the company is trying to bring down the cost of its portable solution, too. Ideally, Acterna would like to make inroads into the multimode cable installation market with an OTDR that costs around $4,000. But Laserriere admits Acterna is far from reaching its goal. Its present OTDR for singlemode cable installation sells for about $10,000.
But Acterna is not attempting to bring down the size of its product too much. If the screen is too small, many events may appear close together and appear as a single event. "You want to bring down the size of the OTDR, but the most important thing is the display itself," says Laserriere.
Acterna's next model of the Media Test Set (MTSe) will combine OTDR with spectral analysis, polarization mode dispersion, and chromatic dispersion functions in a single unit. This solution for wide-scale deployment of high-speed networks will be announced in March. The MTSe's dual-slot design will let field technicians simultaneously enable all of these functions with one unit, which will reduce the number of test instruments that must be carried into the field.
The MTSe's new test functions will let field technicians fully characterize or qualify fiber links to ensure that the fiber can support planned services. Combined chromatic dispersion and OTDR functions will be available in a new four-wavelength 1310/1480/1550/1625 nm module. A new PMD module will let technicians qualify fiber links for high bit rate transmissions up to 10 Gbits/sec.
Brian Milligan is senior associate editor for Cabling Installation & Maintenance.