OTDRs add features, improve performance

Jan. 1, 1998
Optical time-domain reflectometers (OTDRs) are finding ever-increasing use in premises and campus networks as optical fiber has become the medium of choice for backbone applications and gradually makes its way to the desktop for high-performance tasks.

Lynn Haber

Optical time-domain reflectometers (OTDRs) are finding ever-increasing use in premises and campus networks as optical fiber has become the medium of choice for backbone applications and gradually makes its way to the desktop for high-performance tasks.

As demand picks up, major otdr manufacturers--including Anritsu Corp. (Richardson, TX), Antel Optronics Inc. (Richardson, TX), EXFO Electro-Optical Engineering Inc. (Vanier, QC, Canada), Hewlett-Packard Co. (Colorado Springs, CO), Laser Precision Div. of GN Nettest (Utica, NY), Photon Kinetics Inc. of York Technologies Ltd. (Beaverton, OR), Siecor Corp. (Hickory, NC), and Tektronix Inc. (Beaverton, OR)--are adding new features and improving performance in both their mainframe and mini-otdr product lines.

For example, Valerie Dyhouse, product marketing manager at Photon Kinetics, sees a trend toward adding bidirectional averaging capability to these devices. This trend is driven by the increasing demands made on contractors for comprehensive documentation. The need to provide contractors with the ability to manipulate date is also driving the importance of emulation software, which allows users to do a batch reading and export the information to spreadsheets or other applications at the office.

For ease of use, the manufacturer has minimized the number of buttons on its models and has also implemented a track-pad interface. A mouse or keyboard port is also available. The modules cost $12,000 to $25,000.

Siecor offers the OTDR Plus Multitester, which provides multimode and singlemode otdr capabilities, a power meter, a visual fault locator, and a singlemode stabilized laser source. Siecor`s philosophy on modularity is the hard-wire approach--no swapping out modules--which proponents say minimizes failures. That means customers order the otdr to their specifications. Additional upgrades can be requested from the factory. The manufacturer offers 10 OTDR Plus Multitester Options for singlemode-only, multimode-only, and both singlemode and multimode testing. Pricing varies depending upon configuration.

Tektronix recently introduced enhancements to its TekRanger mini-otdr to provide even more-reliable and repeatable measurements, which are traceable to the National Institute of Science and Technology (NIST) standards. Many OTDR manufacturers limit their accuracy specifications to hardware performance only. However, event-marking software has become an integral part of the performance of most OTDRs. With its TekRanger 2 mini-OTDR, Tektronix specifies the system-level accuracy of the instruments, which takes into account both hardware and software performance. Its system measurement accuracy--verified on a 16-km nist traceable calibration system--is plus or minus4 meters for distance and plus or minus0.01 dB for loss.

Noyes Fiber Systems (Laconia, NH) offers the ofl100 OTDR, which is a modified optical-fault locator. It gives a text description of the fiber minus the picture. The product started out as an optical-fault locator, but has been modified to accommodate singlemode and multimode fiber, store up to 98 traces, and provide dos data storage.

By removing the display and acquisition technology, the manufacturer can offer users a low-cost test instrument, says Ryan Irving, regional sales manager and application engineer at Noyes. "Our product is for the budget-minded contractor who needs a less expensive way to do otdr [testing]," he says. If the user doesn`t mind giving up the display or real-time mode, the unit can be purchased for $5000 to $7500.

A trend that has so far found little success is remote OTDR testing. Instead of companies having to send someone out to the field to perform fiber testing, a remotely installed otdr can do it automatically. Industry interest in remote or unattended testing is being driven by network manager concerns for high data rates or rerouting, if necessary.

Remote monitoring is achieved by installing a telecommunications crossconnect and hooking it up to an OTDR to take measurements unattended. The remote device must be intelligent enough to recognize which fiber it is connected to and measure its attributes. The system would automatically dial up technical support or the central office with test output. Anritsu Wiltron recently introduced remote monitoring capability on its MW9070B product.

Manufacturers believe that technological improvements are making remote monitoring more feasible and expect to see the trend toward remote monitoring systems gain steam.

OTDR products are available through distributors or vendor-direct. Although most products are designed to be intuitive, manufacturers recommend a short training period for new users of OTDR equipment and will offer hands-on training. The learning curve is not steep, and new users can expect to be up and running in a couple of hours.

Lynn Haber is a freelance writer specializing in networking and telecommunications issues.

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