Test and measurement specialist OptoTest wants to make sure its customers are aware of a pending update to the Telecommunications Industry Association (TIA) FOTP-171 standard for testing short-length multimode graded-index and singlemode fibre cable assemblies.
Though the changes are not dramatic, they will require new test conditions to enable more consistent and accurate test results, according to OptoTest. Encircled flux launch condition requirements will be added to certain types of test, for example. The updated standard will also clarify the conditions for testing bend-insensitive multimode fibre (BIMMF).
The TIA will specify that the launch reference cord should be constructed with standard, non-bend-insensitive fibre, even when the device under test is bend insensitive. If a receive cord is used, then the fibre type should match the fibre of the device under test.
One reason for this change is that the use of a bend-insensitive launch cord affects the test results, even when the reference cord and source are conditioned for encircled flux. The insertion loss can be as much as 0.1dB higher, and this will make it more difficult for manufacturers and installers to meet the requirements for low-loss (<0.25dB) cable assemblies.
OptoTest wants to reassure its customers that it will continue to manufacture and supply high-quality non-BIMMF reference cords for OM2, OM3, OM4, and OM5 cables. This will address concerns in the industry that non-BIMMF – and the reference cables made from it – is becoming increasingly hard to find. At least one fibre manufacturer has made a commitment to continue to manufacture non-BIMMF fibre in order to address the need for reference cables.
It is likely that the International Electrotechnical Commission (IEC) will adopt similar language regarding the use of non-BIMMF reference cords, OptoTest adds.
OptoTest’s Application Note AN-125 on bend-insensitive multimode fibre (BIMMF) addresses the topic in greater detail.