Fast tunable optical filter using cascaded Mach-Zehnder Interferometers with apodized sampled gratings

We demonstrate a novel tunable optical filter using cascaded Mach-Zehnder interferometers with apodized sampled gratings (ASGs). The ASGs are fabricated using an InGaAsP-InP deep-ridge waveguide with vertical-groove surface grating to obtain a high extinction ratio by sidelobe suppression. The proposed filter exhibits the total free-spectral range of 16 nm, an extinction ratio of 20 dB, and a 3-dB transmission bandwidth of 32 GHz.

I. Introduction

The increase in transmission capacity has led to the need for high-throughput routers. Photonic packet switches based on wavelength-division-multiplexing (WDM) technology have been reported for high-throughput switching in a WDM network [1], [2]. Fig. 1. Schematic diagram of the tunable optical filter. They normally utilized a fast tunable optical filter for packet-by-packet selection of optical packets with different wavelengths. An example of these types of filter is arrayed waveguide grating filters integrated with semiconductor optical amplifier gate switches [3]. Although the characteristics of such optical filters meet the requirements in terms of insertion loss, crosstalk, and switching speed, there still remain essential challenges in cost and compactness.