Principles for commissioning the optical power of a network carrying both coherent and non-coherent wavelengths

4

Principally, a coherent network can be commissioned in the same way as a non-coherent network, without considering fiber access scenarios. In a scenario in which 100G coherent wavelengths need to be added on a non-coherent network for capacity expansion, the incident optical power can be reduced to increase the OSNR tolerance of the 100G wavelengths and the transmission distance without electrical regeneration. In this situation, the optical power of single non-coherent wavelengths will be definitely reduced. When this occurs, commission the network according to the network design.

Other related questions:
Differences in commissioning a non-coherent system and a coherent system
The main difference in commissioning a non-coherent system and a coherent system is the position of the transmit-end EVOA. In a coherent system, the transmit-end EVOA is always located after the OA board. In a non-coherent system, the transmit-end EVOA is located after the OA board only in the non-standard fiber access mode.

Method used to distinguish coherent boards from non-coherent boards
40G boards have both coherent and non-coherent boards. All 100G boards are coherent boards. The following lists the coherent and non-coherent 40G boards, and 100G boards that are applicable to the OSN 8800: 40G coherent boards: TN15LSXL, TN55NS3, TN56NS3, TN54HUNS3 40G non-coherent boards: TN11LSXL, TN12LSXL, TN11LSXLR, TN12LSXLR, TN11LSQ, TN11LSQR 100G coherent boards: TN12LSC, TN14LSC, TN11LTX, TN12LTX, TN54NS4, TN56NS4

Reason why a coherent system uses fewer OA boards than a non-coherent system
OA boards are used to compensate for insertion loss. Only one OA board is required in case that Gmax (maximum gain) �?Fiber loss + DCM loss; otherwise, two OA boards are required. The coherent system does not require DCMs, and a single OA board can compensate for larger link loss. When the link loss is within the permitted range, the coherent and non-coherent systems require the same number of OA boards. When the fiber loss is out of the permitted range, the coherent system, however, requires fewer OA boards. For example, in a system with a 60 km span, 18 dB fiber loss, and 5 dB DCM loss: The gain required by a coherent system is calculated as follows: Gain = Fiber loss + DCM loss = 18 dB + 0 dB (no DCM) = 18 dB < Gmax. Therefore, one OA board (OAU101) is required. The gain required by a non-coherent system is calculated as follows: Gain = Fiber loss + DCM loss = 18 dB + 5 dB = 23 dB < Gmax. Therefore, one OA board (OAU101) is required. In a system with a 100 km span, 28 dB fiber loss, and 9 dB DCM loss: The gain required by a coherent system is calculated as follows: Gain = Fiber loss + DCM loss = 28 dB + 0 dB (no DCM) = 28 dB < Gmax. Therefore, one OA board (OAU101) is required. The gain required by a non-coherent system is calculated as follows: Gain = Fiber loss + DCM loss = 28 dB + 9 dB = 37 dB > Gmax (36 dB for an EDFA board). Therefore, two OA boards (OAU101 and OBU101) are required.

Difference in the CD and PMD processing mechanism between a coherent system and a non-coherent system
100G/40G ePDM-BPSK systems are coherent systems. They use DSP chips for coherent detection, delivering superior performance in mitigating dispersion. Therefore, no DCM is required in these systems for dispersion compensation. For 40G DQPSK systems and other non-coherent systems, DCMs are required for dispersion compensation. The DCU board can also be used on the line.

Whether a DCM module intended for a 10G 40-wavelength OTN network can be used in a non-coherent 40G 80-wavelength network
Yes, a DCM module intended for a 10G 40-wavelength OTN network can be used in a non-coherent 40G 80-wavelength network.

If you have more questions, you can seek help from following ways:
To iKnow To Live Chat
Scroll to top