Independent and mixed transmission of 166.5 Gb/s PM-8QAM and 222 Gb/s PM-16QAM Nyquist-wavelength division multiplexed superchannel for long-haul metro network

This paper investigates the Nyquist-wavelength division multiplexed (Nyquist-WDM) terabit superchannel by employing independent and mixed line rate (MLR) transmission of different polarization-multiplexed quadrature amplitude modulation (PM-QAM) subcarriers. Here, terabit superchannel transmission including forward error correction overhead is successfully achieved by employing either 7 x 166.5 Gb/s PM-8QAM or 5 x 222 Gb/s PM-16QAM or both 2 x 166.5 Gb/s PM-8QAM and 3 x 222 Gb/s PM-16QAM simultaneous transmission. Considering linear filtering penalties and nonlinear propagation effects, the proposed superchannel is transmitted over standard single-mode fiber (SSMF) and pure silica core fiber (PSCF) along with erbium-doped fiber amplifier (EDFA) at 19.8- and 15.12-dB span loss for SSMF and PSCF, respectively. The performance of both terabit superchannels is analyzed in terms of maximum reach, good spectral efficiency, highest transmission capacity, and optimum launch power with variation in channel spacing from 50-GHz fixed ITU-T grid to 29 GHz, at an acceptable bit error rate (BER). To achieve BER 4 x 10(-3), MLR-based 166.5 Gb/s PM-8QAM and 222 Gb/s PM-16QAM suffer a penalty of 5.5- and 9.2-dB OSNR over Nyquist-only 7 x 166.5 Gb/s PM-8QAM and 5 x 222 Gb/s PM-16QAM transmission at the advent of a flexible multi-flow transponder. It is observed that at 33.33-GHz Nyquist spacing over PSCF, 5 x 222 Gb/s PM-16QAM and 7 x 166.5 Gb/s PM-8QAM superchannels deliver a reach up to 1800 and 2970 km, while MLR approach results in extreme reach of 2250 and 3600 km over PSCF as per MLR PM-16QAM and PM-8QAM subcarriers, respectively. Hence, an appreciable spectral efficiency-distance product (SEDP) is achieved due to PSCF at Nyquist spacing of 33.33 GHz with 5.25 bit/s/Hz spectral efficiency. A good link power budget is also calculated for the proposed MLR-based Nyquist-WDM superchannel. MLR-based PM-16QAM and PM-8QAM subcarriers deliver excellent SEDP of 11,812 and 18,900 bit/s/Hz center dot km, respectively, which is, to the best of author's knowledge, better on comparing with the other existing literature for single-core channel explorations.