Sumanta Gupta

All-optical 40 Gbits/s packet regeneration by means of cross-gain compression in a semiconductor optical amplifier.

We experimentally demonstrate all-optical reshaping of 40 Gbits/s packets by using cross-gain compression in a semiconductor optical amplifier (SOA). This scheme, which is based on cross-saturation effects between two conjugate signals copropagating in a single SOA, is wavelength preserving and polarization independent and does not suffer from any transient effect at packet edges. We report evidence of noise redistribution and packet reshaping by means of the bit-error rate versus threshold measurements for different input optical signal-to-noise ratios.

Reach Extension of a DPSK Optical Link Using an Optical Filter Demodulator and MLSE Receiver

We have proposed a novel scheme based on chirped fiber Bragg grating (CFBG) as a narrowband optical filter demodulator and a maximum likelihood sequence estimation (MLSE) receiver to attain an enhanced unrepeatered reach in a nonreturn-to-zero differential phase-shift-keying (NRZ-DPSK) transmission link. An extended reach up to 500 km with only 2-dB optical signal-to-noise ratio penalty is found feasible for a 10.7-Gb/s NRZ-DPSK link with the CFBG-MLSE combination.

Operational Equivalence of Self-Switching in MZI and Nonlinear Polarization Switches Based on SOAs

Numerical simulations and experiments demonstrate the equivalence of two self-switches based on semiconductor optical amplifiers, namely the nonlinear polarization switch and the Mach-Zehnder interferometer. This equivalence is highlighted by introducing a one-to-one functional similarity among the switch components. By means of a detailed study on gain and phase difference variations in both switches, we introduce a method to determine the configurations in which the switches exhibit an equivalent power transfer function. Their operational equivalence is experimentally confirmed.

Experimental Characterization of SOA-Based Wavelength Converters for DPSK Signals

We report a detailed experimental characterization of the wavelength conversion of 10 Gb/s non-return-to-zero differential phase shift keying (NRZ-DPSK) optical signals based on four wave mixing (FWM) in a semiconductor optical amplifier (SOA). The performance of this coherent wavelength converter is compared with theoretical results and found to perform better, in terms of extended range of signal-to-pump ratio (SPR) with lower power penalty, than conventional on-off keying (OOK) and return-to-zero DPSK (RZ-DPSK) signals due to its constant envelope and inherent immunity to data pattern fluctuations.

DPSK Packet-Level Power Equalization by means of Nonlinear Polarization Rotation in an SOA

We experimentally characterized at 10 and 40 Gb/s the optical packet power equalization capability of the non-linear polarization-rotation effect in an SOA. We found at 40 Gb/s a maximum input dynamic range tolerance of 12 dB.

All-optical packet power equalizer using nonlinear micro-ring resonator

We have proposed an all-optical packet power equalizer using launched power induced self-switching effect in a nonlinear micro-ring resonator (MRR) operating at 2.5 Gbps. Utilizing the Kerr nonlinearity induced change in the transfer function an of optimally designed MRR based self-switch, an equalization range of 6 dB is reported.

Operational Equivalence of Self-Switching Effect in SOA-based Nonlinear Polarization and MZI Switches

Analysis and detailed simulations show the operational equivalence of two semiconductor optical amplifier (SOA) assisted self-nonlinear switches, namely the nonlinear polarization switch (NPS) and the SOA-Mach-Zehnder Interferometers (SOA-MZI). Under proper conditions, both switches, although physically different, have similar functional features, such as the power transfer characteristics, the gain and the phase difference.

Silicon micro-ring resonator based 16-QAM modulator for WDM transmission systems

In this paper a silicon micro-ring resonator assisted 16-QAM modulator suitable for WDM application has been proposed. We have demonstrated successful operation of the proposed 16-QAM modulator operating at 10 Gbps and 20 Gbps bit-rate per channel for a three channel WDM system. The performance of the modulator for different channel separation has also been investigated using detailed numerical simulations.

Silicon micro-ring assisted WDM modulator for flexible modulation format

We have proposed a silicon micro-ring based WDM modulator, which can simultaneously transmit data in BPSK, QPSK, and 16QAM modulation formats over different WDM channels. Here, we have considered two cases of a three channel WDM system, one with 50GHz channel spacing and another with 100GHz channel spacing. We have shown using numerical simulations the efficacy of simultaneous generation of 10Gbps BPSK, 20Gbaud QPSK, and 20Gbaud 16QAM over three WDM channels. We have analyzed the eye diagrams and signal constellations of different modulation formats both at back-to-back condition and after transmission over few tens of kilometers of standard single mode fiber.

Simultaneous Demodulation and CD Compensation using Optical Ring Resonator under Nonlinear Transmission

We have analyzed the performance of optical ring resonator based DPSK demodulator and CD compensator in a transmission channel having linear and nonlinear impairments. Performance of various DPSK demodulators have been compared with proposed ORR based DPSK demodulator.