Gil Cohen

Spatial Superchannel Routing in a Two-Span ROADM System for Space Division Multiplexing

We report a two-span, 67-km space-division-multiplexed (SDM) wavelength-division-multiplexed (WDM) system incorporating the first reconfigurable optical add-drop multiplexer (ROADM) supporting spatial superchannels and the first cladding-pumped multicore erbium-doped fiber amplifier directly spliced to multicore transmission fiber. The ROADM subsystem utilizes two conventional 1 × 20 wavelength selective switches (WSS) each configured to implement a 7 × (1 × 2) WSS. ROADM performance tests indicate that the subchannel insertion losses, attenuation accuracies, and passband widths are well matched to each other and show no significant penalty, compared to the conventional operating mode for the WSS. For 6 × 40 × 128-Gb/s SDM-WDM polarization-multiplexed quadrature phase-shift-keyed (PM-QPSK) transmission on 50 GHz spacing, optical signal-to-noise ratio penalties are less than 1.6 dB in Add, Drop, and Express paths. In addition, we demonstrate the feasibility of utilizing joint signal processing of subchannels in this two-span, ROADM system.

MEMS wavelength-selective switch incorporating liquid crystal shutters for attenuation and hitless operation

We present the technological merits of combining a high fill factor, one-dimensional, MEMS micro-mirror array for switching and liquid crystal shutters for amplitude control within a wavelength-selective switch (WSS). The combination allows for simplified MEMS actuator design, support for high port counts, high attenuation accuracy, high natural frequency, mechanical robustness against shock & vibrations, and fast switching times. The complexity associated with dual modulating elements at the focal plane is addressed by design choices and optimization of the depth of focus. The WSS is fully Telcordia qualified and carrying live traffic in deployed networks.

Crosstalk in a ROADM supporting spatial superchannels for space division multiplexing

We report crosstalk measurements among spatially-multiplexed subchannels in a ROADM supporting spatial superchannels. Aggregate crosstalk can reach -23dB when express paths are routed on adjacent fibers, but >6dB improvement results when paths are interleaved.

WSS technology for the next generation ROADM networks

This paper presents an overview of the requirements of the next generation dynamic mesh type reconfigurable optical add-drop multiplexer (ROADM) networks carrying optical channels at 100Gb/s and higher data rates. Liquid crystal (LC) and 1-axis Micro-Electro-Mechanical Systems (MEMS) for scalable and flexible wavelength selective switches (WSS) devices for these networks is highlighted.