Use Your OTDR To Test Gigabit Ethernet?

Gigabit testing is the measurement of the data rate, or bandwidth a given piece of fiber cable can handle. Traditional Bit Error Rate Testing.

Traditional Bit Error Rate Testing

Traditionally bit error testing transmits a modulated optical signal with given digital packets of information on one end of the fiber cable and measures the amount information lost in transmission at the other end with an optical receiver. Bit error rate testing or BER is commonly used in a laboratory environment to qualify the fiber cables bandwidth handling capability. The cost of BER equipment and access to both ends often makes BER testing impractical at actual installations. Today's increased bandwidth requirements now make BER testing more critical.

Short Cut Method of Assessing Cable Bandwidth

Another way to determine bandwidth of a given piece of optical cable is by using an Optical Time Domain Reflectometer (OTDR) to measure the cable's length, optical light loss and reflective value. Taking these three values and comparing them to the fiber manufacturer's specifications, assures the user of meeting the fiber's engineered bandwidth.

Example of Fiber Specifications Provided for Meeting 1Gb/s

The difficulty of maintaining a library of fiber specification sheets for hundreds of fiber types and manufacturers while field testing has proven to be unpopular. It is for this reason that installed cable is seldom compared to these three critical parameters or it is simply assumed that the factory supplied bandwidth parameters are attained. When possible, use pulse boxes at both cable ends to assure the connectorized ends are included in collected OTDR test results.

New optical test equipment, such as the FIS Thunderbolt OTDR, stores a library of cable manufacturer's specifications and automatically compares these three critical values. The measured values are displayed and a Pass/Fail indication is shown on the test screen. A failure report is generated to indicate the reason for the failure and to assist technicians in troubleshooting the optical fiber link. As bandwidth requirements increase, it is certain that the test of these three critical elements will lead to a future mandate of this type of field testing. The test will become a valued troubleshooting tool to field technicians in an ever increasing level of optical network complexity.

Contracted cable installations currently require OTDR testing. Unfortunately, many do not perform a comparison test to determine the bandwidth performance of the system. Test equipment needs to keep up with the ever increasing performance tests that are needed to meet the fiber optics industry requirements. Failure reports, such as the one to the left, will become an essential tool to field technicians in finding the root cause of bandwidth test problems. Perhaps specifying that bandwidth parameters are required on your next installation will separate you from the competition. Every Thunderbolt includes a Gigabit Analyzer at no additional charge.

Shows an Example of Fiber Instrument Sales THUDER BOLT OTDR Report