Gigabit per second switching of smart pixel receiver-transmitter pairs

Abstract

Smart pixels are opto-electronic circuits with optical input/output and electronic logic circuits for complex functionality [1]. Arrays of smart pixels can control two dimensional arrays of light beams in high speed, high throughput free space photonic switching systems [2]. An example are the 4x4 arrays of 2x1 embedded control routing nodes, based on GaAs/AlGaAs field-effect-transistor self-electrooptic-effect device (FET-SEED) technology [3], recently used in a five stage switching system [4]. Although this system was operated at 155Mbit/s only, the speeds of smart pixels can be made much higher. One way to achieve increased speeds is by addition of gain stages and the use of larger FETs. However, this makes the receivers and transmitters larger and more dissipative. Another way to increase the switching speed is to use short pulses as optical inputs, which, according to theory [5], considerably reduces the switching time of the receivers. Simple receivers have, indeed, been demonstrated to operate up to 1Gbit/s [6], but receiver-transmitter pairs could only operate up to 650Mbit/s [7]. The speed of the pair was limited by the performance of the transmitter used, which consisted of a FET inverter driving the common node of two modulators connected in series. One can make a faster transmitter by eliminating the load FET and one of the modulators, thus reducing the capacitance and increasing the effective charging current of the modulator. With such a transmitter, and the use of mode-locked pulses in the AROEBICS (Asynchronous Reset On Every Bit for Input Contentionless Switching) method [8], 200ps switching times were recently obtained [9,10]. This result indicated that smart pixels containing this transmitter should be capable of operating in the GHz range. In the present work we use trains of mode-locked laser pulses separated by 1ns to demonstrate the 1GHz operation of a receiver-transmitter pair.