J. E. Simsarian

Optical switch fabrics for ultra-high-capacity IP routers

Next-generation switches and routers may rely on optical switch fabrics to overcome scalability problems that arise in sizing traditional electrical backplanes into the terabit regime. In this paper, we present and discuss several optical switch fabric technologies. We describe a promising approach based on arrayed waveguide gratings and fast wavelength tuning and explain the challenges with respect to technical and commercial viability. Finally, we demonstrate an optical switch fabric capable of 1.2-Tb/s throughput and show packet switching with four ports running at 40 Gb/s each.

Less than 5-ns wavelength switching with an SG-DBR laser

We achieve fast wavelength switching between all channel combinations of a 64-channel sampled-grating distributed Bragg reflector laser in less than 5 ns. The laser was designed to have low tuning currents and efficient heat extraction in order to reduce parasitic thermal effects. We also report on the behavior of the front and back mirror pre-emphasis amplitudes required for the fast switching

Demonstration of the interconnection of two optical packet rings with a hybrid optoelectronic packet router

We demonstrate the interconnection of two optical packet switching systems: a hybrid optoelectronic packet router and two optical packet rings. Error-free inter-ring and intra-ring optical packet transmission and unicast and multicast transport of encapsulated 10 GbE are achieved.

Fast switching characteristics of a widely tunable laser transmitter

We demonstrate a widely tunable laser transmitter that accesses 32 ITU channels with 100-GHz spacing and switches between all channel combinations in less than 45 ns. The compact module uses commercially available electronic components. We investigate the electrical and thermal properties of the laser and the tuning section driver. The experiments show that a low output impedance driver circuit produces faster switching times. Also, temperature variation of the laser limits the wavelength accuracy of the switching. Finally, we present the correlation between switching times and the laser tuning currents.

Wavelength locking a fast-switching tunable laser

We demonstrate wavelength locking in a widely tunable fast-switching laser module that accesses 64 ITU channels with 50-GHz spacing and switches wavelength in under 50 ns. We use a Fabry-Pe/spl acute/rot etalon to stabilize the laser frequency against long-term drifts. We demonstrate locking while continuously switching with random channel schedules of 1-/spl mu/s packets. The locked frequency accuracy of /spl plusmn/3 GHz is a factor of two improvement over operation without locking. We also present the dynamics of the frequency drift due to temperature variation in the laser, and show the correlation between the frequency offsets while locking and the electrical power dissipated in the tuning sections.

Demonstration of a 1.2 Tb/s optical packet switch fabric (32/spl times/40 Gb/s) based on 40 Gb/s burst-mode clock-data-recovery, fast tunable lasers, and a high-performance N/spl times/N AWG

We demonstrate a 1.2 Tb/s optical packet switch fabric based on burst-mode clock-data-recovery at 40 Gb/s with packet separations of up to 400 ns and lock times under 5 ns fast wavelength switching between 32 channels in less than 46 ns and a 42/spl times/42 AWG (array waveguide grating) with a worst-case loss of 4.2 dB.

IRIS optical packet router [Invited]

Feature Issue on ConvergenceWe present a load-balanced packet router with an all-optical data plane and a decentralized control plane. The router, whose architecture scales up to 256 Tbit/s with current technology, consists of two space switches based on wavelength converters and large N×N arrayed-waveguide gratings, surrounding a deterministic time buffer. First experimental results have been obtained in a 2×2 testbed with 40 Gbit/s wavelength converters that use monolithically-integrated semiconductor optical amplifiers, and with fiber-delay-line time buffers.

Compact All-InP Laser-Vector-Modulator for Generation and Transmission of 100-Gb/s PDM-QPSK and 200-Gb/s PDM-16-QAM

A compact indium phosphide (InP)-based integrated transmitter assembly consisting of a tunable laser and a double-nested Mach-Zehnder modulator (vector modulator) was successfully used for the generation of Nyquist-prefiltered quadrature phase shift keying (QPSK) and 16-ary quadrature amplitude modulation (16-QAM) signals at 32 Gbaud. With external polarization division multiplexing (PDM) emulation and digital coherent detection, we realized data rates of 128 Gb/s with PDM-QPSK and 256 Gb/s with PDM-16-QAM from a commercially available small-form factor device originally designed for 40-Gb/s direct-detection differential QPSK applications. We transmitted these two signals over 8000 and 960 km of standard single mode fiber, respectively. We also compared the performance of the integrated transmitter with a LiNbO3 based vector modulator, using a high-performance 100-kHz external-cavity laser and a low-cost 200-kHz to 400-kHz integrated laser assembly as optical local oscillators. The all-InP integrated laser-vector-modulator transmitter was found to be a viable solution for long-haul 100 and 200-Gb/s coherent optical transmission systems.

Fast packet routing in a 2.5 Tb/s optical switch fabric with 40 Gb/s duobinary signals at 0.8 b/s/Hz spectral efficiency

We demonstrate error-free 40 Gb/s duobinary packet routing by fast wavelength switching on two ports in a 64/spl times/64 passive optical switch fabric. Switching in less than 45 ns for all channel combinations and burst-mode clock recovery in less than 15 ns are achieved.

Improving the switching performance of a wavelength-tunable laser transmitter using a simple and effective driver circuit

We report a simple and effective method to reduce the switching time of a semiconductor tunable laser. We perform simulation and experiment to investigate the limitation in achieving fast switching. A low output-impedance driver is used to effectively reduce the settling time of the diode current of the laser tuning section.