50-GHz-Spacing Athermal Mach–Zehnder Interferometer-Synchronized Arrayed-Waveguide Grating With Improved Temperature Insensitivity

We describe a technique designed to compensate for the residual temperature sensitivity of an athermal silica-based arrayed-waveguide grating (AWG) and its application to a 50-GHz-spacing multi/demultiplexer with a low loss and a wide passband. The device has a Mach-Zehnder interferometer (MZI)-synchronized configuration, in which the AWG and the MZI are athermalized with resin-filled grooves. The point is that we employ a temperature-dependent phase-generating coupler (TD-PGC) in the MZI to compensate for the second-order temperature dependence of the AWG passband wavelength. The fabricated device exhibits practical characteristics including a low loss of less than 3.5 dB and a wide 0.5-dB bandwidth of 24.1 GHz as well as a reduced wavelength variation of less than 10 pm in a - 5degC to 65degC temperature range.

I. Introduction

Arrayed-waveguide grating (AWG) multi/demultiplexers based on silica-based planar lightwave circuit (PLC) technology play key roles in dense wavelength-division-multiplexing systems. In particular, the extension of systems employing reconfigurable optical add–drop multiplexers (ROADMs) [1], [2] has generated a need for AWGs with a lower loss and a wider bandwidth as well as a temperature-insensitive (athermal) characteristic with a view to realizing greater cascadability and reducing electrical power consumption. To respond to this, we have already demonstrated a low-loss and wide-passband athermal AWG with 100-GHz spacing [3], in which we applied an athermalization technique using a resin-filled groove [4], [5] to a Mach–Zehnder interferometer (MZI)-synchronized AWG configuration [6].