360-Gb/s Optical Transmitter With Arbitrary Modulation Format and Dispersion Precompensation

This letter introduces a versatile data-rate and modulation format transparent optical transmitter for 360-Gb/s transmission based on optical arbitrary waveform generation (OAWG) techniques. An experimental implementation of static OAWG, or line-by-line pulse shaping, with a silica arrayed-waveguide-grating pair waveform shaper, demonstrates creation of repetitive time-domain waveforms representing data packets in on-off keying and differential phase-shift-keying modulation formats with optional precompensation for fiber chromatic dispersion (CD). Transmission of repeated 9-bit 360-Gb/s data packets occupying 680 GHz of total optical bandwidth, with CD precompensation over a 10-km single-mode fiber link, indicates the potential for terabit-per-second operation. These data packets have a spectral efficiency of 0.53 b/s/Hz.

I. Introduction

Optical arbitrary waveform generation (OAWG) is a technique for generating truly arbitrary waveforms by parallel intensity and phase modulations of individual spectral lines from an optical frequency comb (OFC) [1]–[3]. Applications for customized optical arbitrary waveforms range from light detection and ranging (LIDAR) to coherent control of both chemical reactions and quantum mechanical wave packets [1] to the generation of high-speed data in various modulation formats [4], [5]. Fig. 1 shows how OAWG manipulates an OFC to generate unique, arbitrary waveforms. First, individual comb lines of an OFC with spacing are spectrally demultiplexed onto isolated spatial locations or waveguides (i.e., channels) using a device such as an arrayed-waveguide grating (AWG). Next, simultaneous intensity and phase modulation is applied separately to each comb line. When these modulations are low frequency or constant it is termed static OAWG, which is also known as line-by-line pulse shaping. Finally, the modulated comb lines are multiplexed onto a single spatial location or waveguide, yielding the shaped waveform. The completely specified spectral intensity and phase uniquely defines the time domain waveform via the Fourier transform and the total OFC bandwidth determines the minimum temporal feature size. In static OAWG, the shaped waveform repeats at the OFC repetition rate , and its duration is limited by the OFC period . However, in dynamic OAWG, the modulations are rapidly varying , thereby changing the waveform each OFC period to potentially create extended duration waveforms. By using moderate modulation bandwidth (10 GHz) with a moderate number of comb lines (), very high bandwidth (1 THz) arbitrary waveform generation is possible. Work is in progress to realize dynamic OAWG on the InP platform [6], [7]. Fig. 1.

OAWG methodology involves the manipulation of the spectral intensity (arrows) and phase (×) of optical comb lines with a total bandwidth of , to produce the desired temporal intensity (blue) and phase (red). In static OAWG, the shaped waveform repeats every .