Suhas Bhandare

First Real-Time Data Recovery for Synchronous QPSK Transmission With Standard DFB Lasers

For the first time, synchronous quadrature phase-shift keying data is recovered in real-time after transmission with standard distributed feedback lasers using a digital inphase and quadrature receiver. Forward-error-correction-compatible performance is reached at 800 Mb/s after 63 km of fiber. Self-homodyne operation with an external cavity laser is error-free

5.94-Tb/s 1.49-b/s/Hz (40/spl times/2/spl times/2/spl times/40 Gb/s) RZ-DQPSK polarization-division multiplex C-band transmission over 324 km

The combination of return-to-zero differential quadrature phase-shift keying with polarization-division multiplex, a 16-ary modulation scheme, allows for ultimate spectral efficiency. We raise C-band fiber capacity with phase-shift keying transmission beyond previously reported figures, achieving forward-error correction limit performance over four fiber spans.

Coherent Digital Polarization Diversity Receiver for Real-Time Polarization-Multiplexed QPSK Transmission at 2.8 Gb/s

This letter presents a coherent digital polarization diversity receiver for real-time polarization-multiplexed synchronous quadrature phase-shift keying transmission with distributed feedback lasers at a data rate of 2.8 Gb/s. The tolerance against fast polarization changes and polarization-dependent loss is evaluated for different filter widths in the carrier recovery circuit. The minimum achieved bit-error rate is 3.4 times 10-7.

Frequency and Phase Estimation for Coherent QPSK Transmission With Unlocked DFB Lasers

This letter presents a hardware-efficient frequency estimator and an advanced phase estimation algorithm capable of tracking the phase noise of a 10-GBaud optical quadrature phase-shift-keying transmission system with standard distributed-feedback lasers in the presence of a frequency mismatch up to 1.2 GHz. This algorithm allows us to implement a digital coherent receiver without an analog frequency control circuit.

1.6-b/s/Hz 160-Gb/s 230-km RZ-DQPSK polarization multiplex transmission with tunable dispersion compensation

A 160-Gb/s (4/spl times/40 Gb/s) return-to-zero differential quadrature phase-shift keying polarization-division multiplex transmission is demonstrated with Q>15.6 dB in one of eight 100-GHz-spaced wavelength-division-multiplex channels after 230 km of fiber. Residual chromatic dispersion (CD) is equalized by a thermally tunable CD compensator for the 192.5-THz channel. Polarizations, in-phase and quadrature data channels are demultiplexed using a LiNbO/sub 3/-based automatic polarization control and a 1-bit interferometer, respectively.

Novel nonmagnetic 30-dB traveling-wave single-sideband optical isolator integrated in III/V material

Various attempts have been made to fabricate waveguide-type isolators in III/V material by implanting magnetic materials, but none of them has so far resulted in a commercial product. Here, we report for first time on an integrated optical isolator implemented in III/V material. It consists of a single-sideband electrooptic modulator where traveling electrical waves make the transmission direction-dependent. Isolation is 30 dB, excess insertion loss is 8 dB. Residual rms ripple is 7% for peak-to-peak RF driving amplitudes of 3.5 V at 4.0 GHz. The estimated transmission penalty for 40 Gb/s return-to-zero differential phase shift keying (RZ-DPSK) signals is 0.2 dB (0 dB measured).

Ultra-Fast Adaptive Digital Polarization Control in a Realtime Coherent Polarization-Multiplexed QPSK Receiver

A digital polarization control system integrated in a 2.8 Gbit/s realtime polarization-multiplexed coherent QPSK system compensates for endless polarization changes having a maximum gradient of 3.5 krad/s (12 krad/s) with 1 dB (3.9 dB) loss in receiver sensitivity.

PDL-Tolerant Real-time Polarization-Multiplexed QPSK Transmission with Digital Coherent Polarization Diversity Receiver

This paper presents the implementation of a real-time electronic polarization tracking algorithm which enables robust optical polarization-multiplexed synchronous quadrature phase shift keying transmission with DFB lasers. The achieved BER at a data rate of 2.8 Gbit/s is well below the FEC threshold.

Performance of 20 Gb/s quaternary intensity modulation based on binary or duobinary modulation in two quadratures with unequal amplitudes

2times10 Gb/s quaternary intensity modulation signals (4-IM) can be generated by combining two modulation signals with unequal amplitudes in quadrature phases or orthogonal polarizations. Two 10-Gb/s nonreturn-to-zero (NRZ) amplitude-shift keying (ASK) signals and a quadrature phase-shift keying (QPSK) modulator allow to generate 4-IM with the same bandwidth as an NRZ-ASK signal (QASK). Measured sensitivity at a bit error rate (BER) of 10-9 and chromatic dispersion (CD) tolerance are -21.6 dBm and ~+130 ps/nm, respectively. Two duobinary 10-Gb/s data streams and a QPSK modulator allow to generate a 9-constellation point quaternary intensity signal (QDB), with the same bandwidth as a duobinary signal. A stub filter with frequency response dip at 5 GHz was used to generate the duobinary signals. Detected as a 4-IM, this scheme features a sensitivity and a CD tolerance of -21.2 dBm and ~+140 ps/nm, respectively. By combining the two duobinary 10-Gb/s data streams with unequal amplitudes in orthogonal polarizations, a 9-constellation point quaternary intensity signal was also obtained (QPolDB). Sensitivity and CD tolerance were -20.5 dBm and ~+340 ps/nm, respectively. They became -18.4 dBm and ~+530 ps/nm, respectively, when the frequency response dip of the stub filter was changed to 6 GHz. A polarization and phase-insensitive direct detection receiver with a single photodiode has been used to detect all generated quaternary signals as 4-IM signals

1.6 Gbit/s Real-Time Synchronous QPSK Transmission with Standard DFB Lasers

Using standard DFB lasers, 1.6 Gbit/s QPSK data is demodulated and recovered coherently and synchronously in real-time, faster than ever before. BER after 63 km of fiber is well below the FEC threshold.