The Performance of The OTDR For FTTH And Index Requirements

In view of the FTTH fiber optic lines are not long distance, so the OTDR’s also different from the index requirements for long distance test, so i think: basic on FTTx test OTDR, its should be small size, light weight, small blind of events, ranging high resolution, long battery life, and easy to carry, the targets require reference to the following:

Dynamic range: 20/24dB（850nm/1300nm，multimode fibre);
32/30/30dB (1310nm/1550nm/1625nm, singlemode fiber);
Event Dead Zone: ≤2m;
Range resolution:≤0.1m;

OTDR the most important indicators is the dynamic range, reflecting its ability to detect long distance fiber optic lines, under the same conditions, the dynamic range is greater the longer the distance you can detect fiber, the dynamic range of the size of both the work and the OTDR wavelengthits emitted light pulse width, and generally speaking the dynamic range of the OTDR are means under the conditions of a pulse width of maximum light. The OTDR applied the FTTH line test, does not require a large dynamic range, generally speaking, a test of the multi-mode fiber, 20/24dB (850nm/1300nm) enough; testing of the single-mode optical fiber, and 32dB (1310 /1550nm/1625nm) had to meet actual use.

The event dead zone is an important indicator of OTDR, reflect a OTDR’s ability to detect short-distance optical fiber. The test blind smaller, ranging higher the resolution, the fiber optic cable of the point and the point of failure of the events in higher positioning accuracy. Dynamic range OTDR event dead zone size has a direct relationship with the optical pulse width, the pulse width becomes narrower, the smaller the possible event blind. General OTDR event dead zone indicators are under specific test conditions, such as minimum test pulse width, facet reflectivities ≤ 40dB. FTTH fiber link testing, OTDR event dead zone is less than 2m.

USB interface is very necessary for OTDR terms of market many brands OTDR some configuration floppy drive, floppy disk storage; as well as the configuration of the PCM card, but this is very inconvenient, the truth is verysimple: the poor durability of the floppy disk, take a few times to be scrapped, and can work properly only temperature range 5 ° C to 35 ° C, another storage capacity is not big enough, only 1.44Mbytes deposit not pieces of waveform; PCMslightly larger capacity cards, but inconvenient to use, you need to purchase the appropriate card reader, which can require the user to dig their own pockets. In contrast, OTDR with USB interface is very convenient, plug-and-play, reliability since Needless to say, it is a floppy disk can not be compared to the storage capacity is very large, even by the currently popular on the market 128M minimum capacity , thousands of waveform storage is absolutely no problem.

Battery powered is also an aspect can not be ignored, workers, taking into account the testing FTTH fiber optic lines, are longer require battery-powered, currently on the market each OTDR say their battery-powered timelong, and the working conditions of the same: plenty of standby time, some continuous test of time as well as test time of one minute every 5 minutes, even worse is the working time of the two battery packs. Optional OTDR can not just battery time, but also to understand under what conditions they are not to be misled.