We studied 2 types of polarization insensitive semiconductor optical amplifier (SOA) gates for use in wavelength division multiplexing (WDM) applications: 1) a low operation current SOA gate with a small and square bulk active region but without spot-size converters and 2) a multi channel SOA gate array with tapered waveguide spot-size converters (SS-SOA) on both sides. The low operation current SOA gate provided a very low current for fiber-to-fiber loss-less operation (5. 4-7. 0 mA) and a high extinction ratio (>30 dB) over a wide wavelength range (1530-1580 nm). For multi channel array assembling, the SS is indispensable. The 4-channel SS-SOA gate array was assembled on a planar lightwave circuit (PLC) platform for the first time. The gain characteristics of each channel were very similar and a low fiber-to-fiber loss-less current of 33 mA and a high extinction ratio of nearly 40 dB were achieved in all channels. The polarization dependence was less than 1 dB. Using the fully packaged 4-channel hybrid gate array module (a 4 channel SS-SOA on PLC platform), an ultra-wide-band (1530-1600 nm) high speed wavelength selector was successfully demonstrated. Both rise- and fall-times were less than 1 ns, which makes the wavelength selector suitable for high-speed optical packet switching. Electrical and optical interference between channels were negligible.