Time Resolved Bit Error Rate Analysis of a Fast Switching Tunable Laser for Use in Optically Switched Networks

Abstract

Abstract-We investigate the use of different direct detection modulation formats in a wavelength switched optical network. We find the minimum time it takes a tunable sampled grating distributed Bragg reflector laser to recover after switching from one wavelength channel to another for different modulation formats. The recovery time is investigated utilizing a field programmable gate array which operates as a time resolved bit error rate detector. The detector offers 93 ps resolution operating at 10.7 Gb/s and allows for all the data received to contribute to the measurement, allowing low bit error rates to be measured at high speed. The recovery times for 10.7 Gb/s non-return-to-zero on-off keyed modulation, 10.7 Gb/s differentially phase shift keyed signal and 21.4 Gb/s differentially quadrature phase shift keyed formats can be as low as 4 ns, 7 ns and 40 ns, respectively. The time resolved phase noise associated with laser settling is simultaneously measured for 21.4 Gb/s differentially quadrature phase shift keyed data and it shows that the phase noise coupled with frequency error is the primary limitation on transmitting immediately after a laser switching event.

Fast Reconfigurable SOA-Based Wavelength Conversion of Advanced Modulation Format Data

“…Around 11 nm tuning range can be achieved for the wavelength conversion of PM-QPSK data to get a BER value below the 7% FEC limit. In order to investigate the time-resolved BER [57,58] performance of the fast-reconfigurable wavelength converter, we apply a square wave current with 500 kHz repetition rate to the front section of the SGDBR to switch the wavelength converted idler between Ch1 (1541.395 nm) and Ch2 (1538.684 nm), with the other currents applied to the SGDBR laser held constant and the received OSNR set at 12 dB for the QPSK signal and 14.5 dB for the PM-QPSK signal. The time-resolved BER measurement is characterized for Ch1 by fixing the center frequency of the OBPF to Ch1 and adjusting the LO to the wavelength of Ch1.…”

Multiplier-Free Joint Carrier Recovery for 16-QAM Synchronous or Agile Burst Receivers

“…For coherent agile burstreceiver applications, it is critical to tolerate large and rapid CFO swings during the burst transients of the LO. In these prior coherent burst receivers, the CFO tolerance was achieved by adopting simple soft differential [4], [6], [13] or doubly differential [12] decoding (as opposed to 'hard' or 'logical' differential decoding, ahead of the slicer [14]). However each phase soft differencing at least doubles the ASE noise, thus substantial OSNR penalty is incurred in those current approaches.…”

“…We simulated coherent reception with the proposed CR for a 16-QAM single channel, with Tx DP as per [4], [6], [13], propagating through a scalar fiber link model comprising ASE white noise, laser phase noise from the Tx and LO sources having combined effective linewidth (LW) ν /R s = ν LW T s and CFO ν C F O ≡ ν C F O /R s , both normalized by the R s = 25 Gbaud baudrate. One million symbols were simulated.…”

Dual-wavelength source based optical circuit switching and wavelength reconfiguration in multi-hop ROADM systems

“…A tunable sampled grating distributed Bragg reflector (SG-DBR) laser was used to switch between a pair of wavelengths, modulated with different modulation formats. The guard band that resulted from the tuning transition was evaluated to be 4 ns, 7 ns, and 40 ns, for 10.7 Gb/s NRZ-OOK, 10.7 Gb/s DPSK and 21.4 Gb/s DQPSK respectively [19].…”