Differences between G.653 and G.655 fibers in fiber measurement

Question:
Fiber measurement is usually required in engineering commissioning of 40G WDM and 10G WDM systems. In guide documents, parameters to be measured are attenuation, CD value, and PMD value. In practice, zero dispersion slope is also an important parameter that must be measured. This parameter can be used to distinguish between G.653 fibers and G.655 fibers.
Analysis:
Understanding how to distinguish between G.653 fibers and G.655 fibers through fiber measurements is important because the two types of fibers require different incident optical power. G.653 fibers impose strict requirements on incident optical power. If incident optical power does not meet specified requirements, non-linear effects are serious, which results in a high bit error rate (BER), low optical signal-to-noise ratio (OSNR), or even a service interruption.
Root cause:
None
Answer:
The specifications of the two types of fibers are as follows:
1. The G.653 fiber is also called dispersion-shifted fiber. Its typical specifications are as follows:
In the 1310 nm window, the attenuation coefficient is 0.55 dB/km and no typical value is available currently. In the 1550 nm window, the attenuation coefficient is 0.35 dB/km and the value is usually within the range of 0.19 dB/km to 0.25 dB/km. The zero dispersion point is in the range of 1525 nm to 1575 nm and the dispersion coefficient in this range is smaller than 3.5 ps/(nm/km).
G.653 fibers have optimal features in the 1550 nm window and therefore are preferred for single-wavelength and ultra long-haul transmission.
2. The G.655 fiber is also called non-zero dispersion-shift fiber (NZDSF). The zero dispersion point is moved several wavelengths away from 1550 nm so that the zero dispersion point is not in the working wavelength range near 1550 nm.
Its typical specifications are as follows:
In the 1310 nm window, the attenuation coefficient is 0.55 dB/km and no typical value is available currently.
In the 1550 nm window, the attenuation coefficient is 0.35 dB/km and the value is usually within the range of 0.19 dB/km to 0.25 dB/km.
The dispersion coefficient absolute value is between 1.0 to 10.0 ps/(nm/km).
3. According to the preceding specifications, the attenuation coefficient and CD value of G.653 fibers are not very different from those of G.655 fibers. Actually, the value range of the attenuation coefficient and CD value of G.653 fibers overlaps with that of G.655 fibers. The actual specifications of fibers are determined by manufacturers. The PMD value depends on the quality of fibers. Therefore, you cannot distinguish between G.653 and G.655 fibers using only these parameters.
4. In this case, another parameter called maximum zero dispersion slope can be used to distinguish between G.653 and G.655 fibers. This parameter is essential to distinguishing fiber types. Each type of fiber has only a typical zero dispersion slope and the value is not fixed. The change of the value, however, is very small and this parameter is fiber-specific. Take G.653 and G.655 fibers as examples. Zero dispersion slopes of them are as follows:
G.653: 0.07600 ps/(nm^2·km)
G.655-LEAF: 0.08365 ps/(nm^2·km)
G.655-TWRS: 0.04780 ps/(nm^2·km)
You can distinguish between G.653 and G.655 fibers by measuring zero dispersion slopes of them.

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