Aazar S. Kashi

Silicon Microring Modulator for Dispersion Uncompensated Transmission Applications

We report an investigation of the negative-chirp characteristics of an overcoupled silicon microring modulator with carrier-depletion p-n junction for 10-Gb/s transmission over single-mode fiber up to distances of 100 km. The modulator exhibits over 15 dB extinction ratio for an approximately 5 V peak-to-peak driving voltage. The on/off chirp α-parameter is estimated to be less than -1 for an optimally designed device. This negative chirp leads to a robust dispersion tolerance which is verified by bit error rate measurements. The results show that the device can support transmission with a negative power penalty up to 50 km, while the power penalty at 100 km is as low as 2.5 dB.

High Resolution Characterization of the Spectral Broadening Due to Fiber Nonlinearities

Balanced heterodyne detection and a gated microwave spectrum analyzer are used to precisely measure the spectral broadening due to intra-channel fiber nonlinearities. Polarization resolved spectra for a 224 Gb/s dual polarization 16-ary quadrature amplitude modulation signal are quantified in terms of the spectral edge power, which serves as a useful metric for capturing the effects of both fiber nonlinearities and amplified spontaneous emission noise. It is shown that without and with perturbation-based pre-compensation for the signal distortion due to the Kerr effect, the launch powers that minimize the bit error ratio and spectral edge power coincide.

Impact of MAP detection on the mutual information of a 1.2 Tb/s three-carrier DP 16-QAM superchannel

For a 1.206 Tb/s three-carrier DP 16-QAM super channel, the mutual information is evaluated without and with fixed look-up table based maximum-a-posteriori detection at the receiver to mitigate pattern-dependent distortion in the transmitted signal.

Information rates for the SP 128-QAM and DP 16-QAM modulation formats

Information rates for the set-partitioning (SP) 128-QAM and dual-polarization (DP) 16-QAM modulation formats are compared for the same bit rate (256 Gbit/s) and baud rate (32 Gbaud). For 256 Gbit/s transmission over 3600 km, SP 128-QAM offers an increase of 8.2%.

Direct Modulation of a Laser Using 112-Gb/s 16-QAM Nyquist Subcarrier Modulation

A 112-Gb/s single-carrier, single-polarization short reach transmission system using a high bandwidth 1310 nm directly modulated laser is demonstrated. Spectrally efficient signal generation is achieved by using: 1) half-cycle Nyquist subcarrier modulation with 16-ary quadrature-amplitude-modulation; 2) pre-compensation for the frequency response of the end-toend system; and 3) and a Volterra nonlinear equalizer to postcompensate for the nonlinear modulation dynamics of the laser. Digital signal processing techniques for signal recovery enable transmission over 20 km of standard single mode fiber with a bit error ratio below the 7% overhead hard-decision forward error correction coding threshold of 4.6 × 10-3 at a received optical power of -5.25 dBm.

Impact of intra- and inter-subcarrier nonlinearities on the information rate of a 1.206 Tbit/s DP 16-QAM superchannel

For a 1.206 Tbit/s DP 16-QAM superchannel, the impact of the number of subcarriers on the intra- and inter-subcarrier nonlinearities and on the maximum achievable transmission distance for an information rate of 1 Tbit/s is determined by simulation.

Simplified perturbation-based approach for predicting the tolerance to intra-channel nonlinear effects

A broadly applicable perturbation-based approach is demonstrated for estimating the impact of intra-channel fiber nonlinearities on system performance. The estimated performance for DP-QPSK, DP-8QAM, and DP-16QAM exhibits good agreement with both simulation and experimental results.