This paper describes a silica-based 88 strictly nonblocking thermooptic matrix switch with a high-extinction ratio and low loss. We realized this matrix switch by using a configuration which combines a double Mach-Zehnder interferometer (MZI) switching unit and an NN matrix arrangement thus reducing the total waveguide length. The 88 matrix switch was fabricated on a 4-in wafer using planar lightwave circuit technology. We obtained an average extinction ratio of 60.3 dB and an average insertion loss of 5.1 dB. The operating wavelength bandwidth completely covers the gain band of practical erbium-doped fiber amplifiers (EDFA's).
Takashi Goh, Akira Himeno, Masayuki Okuno, Hiroshi Takahashi, and Kuninori Hattori, "High-Extinction Ratio and Low-Loss Silica-Based 88 Strictly Nonblocking Thermooptic Matrix Switch," J. Lightwave Technol. 17, 1192- (1999)