Article

# Multi-Carrier Coherent Receiver Based on a Shared Optical Hybrid and a Cyclic AWG Array for Terabit/s Optical Transmission

Bell Labs., Alcatel-Lucent, Holmdel, NJ, USA

IEEE Photonics Journal (Impact Factor: 2.33). 07/2010; DOI: 10.1109/JPHOT.2010.2047388 Source: IEEE Xplore

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**ABSTRACT:**We investigated through simulations the performance of Nyquist-WDM Terabit superchannels implemented using polarization-multiplexed phase shift-keying based on 2 (PM-BPSK) and 4 (PM-QPSK) signal points or polarization-multiplexed quadrature amplitude modulation based on 8 (PM-8QAM) and 16 (PM-16QAM) signal points. Terabit superchannels are obtained through the aggregation of multiple subcarriers using the Nyquist-WDM technique, based on a tight spectral shaping of each subcarrier which allows very narrow spacing. We first studied the optimum transmitter/receiver filtering in a back-to-back configuration. Then we investigated the maximum reach for different spectral efficiencies, after nonlinear propagation over uncompensated links with lumped amplification. Performance for systems based on both standard single-mode fiber (SSMF) and large effective area non-zero dispersion-shifted fiber (NZDSF) has been analyzed. Assuming SSMF with 25-dB span loss, we found that PM-BPSK can reach 6480 km at a net capacity of 4 Tb/s across the C band. Conversely, PM-16QAM can deliver 27 Tb/s, but over 270 km only. Note that a lower span length, the use of Raman amplification and/or pure silica-core fibers (PSCFs) can significantly increase the maximum reach, but without changing the hierarchy among the performance of modulation formats. We also show that the maximum reachable distance is approximately 2/3 of the one achievable in linear propagation at the optimum launch power, regardless of the modulation format, spacing and fiber type. As additional results, we also verified that the optimum launch power per subcarrier linearly depends on the span loss, varies with the fiber type, but it is independent of the modulation format, and that the relationship between the maximum reachable distance and the span loss is almost linear.Journal of Lightwave Technology 01/2011; 29:53-61. · 2.86 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Terabit/s super-channels are likely to become the standard for next-generation optical networks and optical interconnects. A particularly promising approach exploits optical frequency combs for super-channel generation. We show that injection locking of a gain-switched laser diode can be used to generate frequency combs that are particularly well suited for terabit/s super-channel transmission. This approach stands out due to its extraordinary stability and flexibility in tuning both center wavelength and line spacing. We perform a series of transmission experiments using different comb line spacings and modulation formats. Using 9 comb lines and 16QAM signaling, an aggregate line rate (net data rate) of 1.296 Tbit/s (1.109 Tbit/s) is achieved for transmission over 150 km of standard single mode fiber (SSMF) using a spectral bandwidth of 166.5 GHz, which corresponds to a (net) spectral efficiency of 7.8 bit/s/Hz (6.7 bit/s/Hz). The line rate (net data rate) can be boosted to 2.112 Tbit/s (1.867 Tbit/s) for transmission over 300 km of SSMF by using a bandwidth of 300 GHz and QPSK modulation on the weaker carriers. For the reported net data rates and spectral efficiencies, we assume a variable overhead of either 7% or 20% for forward- error correction depending on the individual sub-channel quality after fiber transmission.Optics Express 01/2015; 23(2). · 3.53 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**We report the generation of fifty 12.5-GHz-spaced optical carriers with high power flatness and stability by using a single-side band (SSB) modulator-based recirculating frequency shifter (RFS). The peak-to-peak power difference and the RMS power difference of the generated carriers are 2.5 and 0.3 dB, respectively. We also experimentally investigate the impact of implementation imperfections on the flatness of the generated carriers. The important factors that contribute to the flatness of the generated carriers are found to be the amplitude balance of two inphase (I) and quadrature (Q) drive signals for the SSB modulator, the time misalignment between the I and Q signals, the accuracy of the $\pi/2$ phase bias of the SSB modulator and the stability of the polarization alignment in the RFS. By carefully controlling all the factors mentioned earlier, we obtain stable operation of 50 frequency-locked carriers; showing that the SSB modulator-based RFS is a promising technique for future terabit per second multicarrier transmission.Journal of Lightwave Technology 04/2011; 29(8):1085-1091. · 2.86 Impact Factor

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