OEMfibers 100G optical transceiver frame structure
1. Customer side optical transceiver
IEEE802.3ba stipulates support for 100GE interface types, that's, 100GBASE-SR10, 100GBASE-LR10, 100GBASE-LR4, and Arista QSFP 100GBASE-ER4 , etc., and defines the transmission distance, fiber type, support rate and corresponding wavelength supported by each kind at length. IEEE 802.3ba defines the rate of 100GE as 103.125Gbit/s. OIF defines two types of CFP: 4 wavelengths (4×25G, 100GBASE-LR4/ER4) and 10 wavelengths (10×10G, 100GBASE-SR10/LR10).
2. Line side optical transceiver
DWDM long-distance transmission is principally limited by physical limitations such as OSNR, dispersion, non-linear effects, PMD and so forth. The allowable dispersion tolerance of the system decreases in proportion to the square of the rate; the DGD tolerance is inversely proportional to the rate. The higher the rate, the smaller the DGD allowed by the system, and the statistical characteristics of the signal polarization change make the PMD optical compensation method practically difficult. In addition, the development trend of the optical transmission system is to further improve the spectrum utilization efficiency of the optical fiber to save optical fiber resources. These limiting factors are closely related to the modulation signal rate. The higher the modulation rate, the more apparent the impact. In order to resolve the above problems, the sending end of the 100G line side optical transceiver uses PM-QPSK modulation technology, and the getting end uses coherent detection technology, DSP technology and FEC soft decision.
The transmitting end uses polarization multiplexing technology, two independent optical polarization states to transport 56GHz business. Each polarization state uses QPSK modulation, that may further decrease the baud rate to 28Gbit/s, reducing the bandwidth requirements of optical/electrical devices, thereby reducing system power consumption and cost.
The receiving end uses coherent getting and electric domain compensation technology. Included in this, DSP chip execution functions consist of CD compensation, PMD compensation, SOP tracking, frequency offset estimation and phase recovery. The coherent balanced optical receiver restores two channels of polarization from the optical signal, and demodulates four channels of phase information from it, converts them into digital signals through A/D, and then performs dispersion compensation through the CD compensation transceiver and PMD through the polarization compensation transceiver. And track the rotation of the line SOP for right polarization demultiplexing, and perform frequency offset compensation and phase recovery, and lastly decide to recover the initial signal, and may also output a soft decision signal to the next FEC decoding transceiver. DSP compensation technology can enhance the OSNR tolerance to almost 6dB, the machine dispersion tolerance can reach 40,000 ~ 60000ps/nm, and the PMD tolerance can reach 25 ~ 30ps.
Soft decision FEC technology is often found in 100Gbit/sWDM system. SD-FEC makes full utilization of the channel output waveform information and applies richer sampling information to determine if the received signal can be "1" or "0", which can offer higher decoding accuracy and improve system performance. For a perfect scenario with 20% overhead, soft-decision decoding could have a theoretical gain performance of just one 1.3dB greater than hard-decision decoding.
IEEE802.3ba stipulates support for 100GE interface types, that's, 100GBASE-SR10, 100GBASE-LR10, 100GBASE-LR4, and Arista QSFP 100GBASE-ER4 , etc., and defines the transmission distance, fiber type, support rate and corresponding wavelength supported by each kind at length. IEEE 802.3ba defines the rate of 100GE as 103.125Gbit/s. OIF defines two types of CFP: 4 wavelengths (4×25G, 100GBASE-LR4/ER4) and 10 wavelengths (10×10G, 100GBASE-SR10/LR10).
2. Line side optical transceiver
DWDM long-distance transmission is principally limited by physical limitations such as OSNR, dispersion, non-linear effects, PMD and so forth. The allowable dispersion tolerance of the system decreases in proportion to the square of the rate; the DGD tolerance is inversely proportional to the rate. The higher the rate, the smaller the DGD allowed by the system, and the statistical characteristics of the signal polarization change make the PMD optical compensation method practically difficult. In addition, the development trend of the optical transmission system is to further improve the spectrum utilization efficiency of the optical fiber to save optical fiber resources. These limiting factors are closely related to the modulation signal rate. The higher the modulation rate, the more apparent the impact. In order to resolve the above problems, the sending end of the 100G line side optical transceiver uses PM-QPSK modulation technology, and the getting end uses coherent detection technology, DSP technology and FEC soft decision.
The transmitting end uses polarization multiplexing technology, two independent optical polarization states to transport 56GHz business. Each polarization state uses QPSK modulation, that may further decrease the baud rate to 28Gbit/s, reducing the bandwidth requirements of optical/electrical devices, thereby reducing system power consumption and cost.
The receiving end uses coherent getting and electric domain compensation technology. Included in this, DSP chip execution functions consist of CD compensation, PMD compensation, SOP tracking, frequency offset estimation and phase recovery. The coherent balanced optical receiver restores two channels of polarization from the optical signal, and demodulates four channels of phase information from it, converts them into digital signals through A/D, and then performs dispersion compensation through the CD compensation transceiver and PMD through the polarization compensation transceiver. And track the rotation of the line SOP for right polarization demultiplexing, and perform frequency offset compensation and phase recovery, and lastly decide to recover the initial signal, and may also output a soft decision signal to the next FEC decoding transceiver. DSP compensation technology can enhance the OSNR tolerance to almost 6dB, the machine dispersion tolerance can reach 40,000 ~ 60000ps/nm, and the PMD tolerance can reach 25 ~ 30ps.
Soft decision FEC technology is often found in 100Gbit/sWDM system. SD-FEC makes full utilization of the channel output waveform information and applies richer sampling information to determine if the received signal can be "1" or "0", which can offer higher decoding accuracy and improve system performance. For a perfect scenario with 20% overhead, soft-decision decoding could have a theoretical gain performance of just one 1.3dB greater than hard-decision decoding.
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