# Differences between G.653 and G.655 fibers during fiber measurement

1121. A G.653 fiber is also called a dispersion shift fiber. The typical parameters of a G.653 fiber in the 1550 nm window are as follows:

Attenuation coefficient for the 1310 nm band: < 0.55 dB/km (Currently, the typical value data cannot be obtained yet.) Attenuation coefficient for the 1550 nm band: < 0.35 dB/km (Currently, the value ranges from 0.19 dB/km to 0.25 dB/km.)

The zero dispersion point is within the wavelength band from 1525 nm to 1575 nm, and the dispersion coefficient in this wavelength band is less than 3.5 ps/(nm/km). Due to the good performance in the 1550 nm window, G.653 fibers become the optimal choice for single wavelengths and ultra-long-haul transmission.

2. G.655 fibers are non-zero dispersion shift fibers. For G.655 fibers, the zero dispersion point is moved by the specified number of wavelengths from the 1550 nm wavelength so that the zero dispersion point is not within the range of DWDM operating wavelength around the 1550 nm wavelength. The typical parameters are as follows: Attenuation coefficient for the 1310 nm band: < 0.55 dB/km (Currently, the typical value data cannot be obtained yet.) Attenuation coefficient for the 1550 nm band: < 0.35 dB/km (Currently, the value ranges from 0.19 dB/km to 0.25 dB/km.)

Dispersion: The absolute value for the dispersion coefficient ranges from 1.0 ps/(nm/km) to 10.0 ps/(nm/km).

3. In conclusion, the attenuation coefficients and CD values do not have obvious limits and they are actually overlapped in the standards. As a result, the specifications of cables vary depending on vendors and the PMD values depend on the cable quality.

Therefore, only the preceding parameters cannot help distinguish between G.653 and G.655 fibers.

4. In this case, another parameter, 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 value changes slightly and varies according to fibers. Use 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)

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

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