Table 2.
Cost metrics of the 200-Gb/s net interface rate per wavelength per polarization detection system with field recovery
| Modulation format | BW per ADC (GHz) | Requirement of stable lasers | Number of ADCs |
|---|---|---|---|
| Coherent (homodyne) | 9.7 | Yes | 2 |
| Coherent (heterodyne) | 19.4 | Yes | 1 |
| CADDa | 16.0 | No | 3 |
| KKb | 31.6 | No | 1 |
| Stokesc | 25.1 | No | 3 |
| Gapped SSBd | 50.2 | No | 1 |
| Interleaved SSBe | 50.2 | No | 1 |
This table is reproduced from ref. 30 and the OSNR is set to 30 dB
aA 10% frequency gap is employed for the CADD receiver, with a CSPR of 8 dB
bThe CSPR is 6 dB for the KK receiver19
cFor the Stokes receiver13, modulated signals are in the X polarization, and the Y polarization is occupied by the carrier, with a CSPR of 0 dB. Since this comparison table is based on single polarization, while both polarizations are loaded with either signals or the carrier for the Stokes receiver, we include a multiplication factor of 2 for the bandwidth. In other words, all the bandwidths should be reduced by half when two polarizations are used to obtain the same net interface rate
dThe frequency gap is as wide as the signal bandwidth, and the CSPR is 0 dB for the gapped SSB scheme15
eOdd-numbered subcarriers are loaded with signals, and even-numbered subcarriers are null. The CSPR is 0 dB for such an interleaved SSB scheme31