Contents Introduction
Reconfigurable optical add/drop multiplexers (ROADMs) are being developed with some urgency to allow the cost-effective construction of optical networks with a certain flexibility. With this background, we have developed variable optical attenuator (VOA) multiplexers (V-AWGs) that we integrated by using silica-based planar lightwave circuits (PLCs) [3], [4]. However, it is still necessary to improve the integration technology to meet the growing demand for an increased channel number, and to reduce both module size and cost. In particular, the integration of monitor photodiodes (PDs) without a size penalty or performance degradation caused by waveguide crossings is a key technological issue when we attempt to realize larger scale integration. To solve this problem, we have already proposed a stacked integration approach that uses micro-mirrors formed on the PLC and CAN packaged PDs and demonstrated a 16-channel V-AWG module with inline power monitors [4]. In this study, we have extended this concept to larger scale integration by introducing a new stacked integration technique that combines our recently developed chip-scale-package (CSP) PDs [3] and an improved micro-mirror fabrication technique. We successfully fabricated a 32-channel reconfigurable optical add multiplexer (ROAM) with tap monitors fully integrated on a single PLC chip. This paper provides a brief description of this module.
