Scenario Description:

Fiber measurements are usually required in engineering commissioning of a 40G WDM or 10G WDM system. According to each guide, parameters to be measured are attenuation, CD value, and PMD value. Actually, zero dispersion slope is also a very important parameter and must be measured and flexibly used. This parameter can be used to distinguish between G.653 fibers and G.655 fibers.

Technical ***ysis:

Understanding how to distinguish between G.653 fibers and G.655 fibers through fiber measurements is very important because the two types of fibers require different incident optical power. Note that G.653 fibers impose strict requirement on incident optical power. If incident optical power does not meet the requirement, 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.

Handling Procedure:


The specifications of G.653 fibers and G.655 fibers are as follows:


1. G.653 fibers, also named dispersion shift fibers (DSF)

The typical specifications in the 1550 nm window are as follows. In the 1310 nm window, the attenuation coefficient is smaller than 0.55 dB/km and no typical value is available currently. In the 1550 nm window, the attenuation coefficient is smaller than 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 thus is preferred for single-wavelength and ultra-long-haul transmission.

2. G.655 fibers, also named non-zero dispersion shift fibers (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 that is near 1550 nm.

In the 1310 nm window, the attenuation coefficient is smaller than 0.55 dB/km and no typical value is available currently. In the 1550 nm window, the attenuation coefficient is smaller than 0.35 dB/km and the value is usually within the range of 0.19 dB/km to 0.25 dB/km. The absolute value of dispersion is in the range of 1.0 ps/(nm/km) to 10.0 ps/(nm/km).
3. According to the specifications of the two types of fibers, 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. Hence, actual specifications of fibers are determined by the manufacturer. The PMD value depends on the quality of fibers. As a result, users cannot distinguish between G.653 and G.655 fibers by using only the preceding 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)


Hence, you can distinguish between G.653 and G.655 fibers by measuring zero dispersion slopes of them

Your input to this thread shall be appreciated!

Very clear explanation of different types of fibers and their specifications, to identify while designing or planning a new optical fiber network.

thanks for sharing such a valuable info

Thanks a million, razzaq and philander,

useful info, thanks for sharing, it cleared my concepts of choosing different types of fiber.

and how to compensate dispersion while designing the network?

yes dispersion is the sensitive issue if you are dealing with 40G and 100G wavelengths.