Experimental Demonstration of High-Throughput Transmission Spectrum Measurement for Electro-Absorption Modulator using the Time-Stretch Method

Summary form only given. High-throughput spectrum measurement is useful for capturing non-repetitive and rare phenomena. Recently, continuous single-shot spectrum measurement using ultrafast optical pulses has been realized by a fiber chromatic dispersion (CD)-based time stretch dispersive Fourier Transform (TS-DFT) method [1-3]. In this method, by slowing down fast optical waveforms using CD, it is possible to measure the spectrum of individual pulses using a realtime digitizer. In this paper, we demonstrate, for the first time, high throughput measurements of the transmission spectrum of electro-absorption optical modulators with 11.7 ns refresh time and 50 pm resolution by using this method. The experimental setup is shown in Fig. 1. We used a passive hybrid mode-locked fiber laser with 84.7 -MHz pulse repetition frequency [4]. The pulse width is below 1 ps and the center wavelength is 1553 nm. The spectrum of pulses was broadened by a supercontinuum (SC) fiber. The 84.7-MHz optical pulse train was input into the EA optical modulator (EAM). This EAM was driven by electrical gate signals from a gate generator which produced 480 ns gating pulses. Due to the gate signal, a part of the optical pulses transmitted through the modulator. Then, each optical pulse was slowed down and chirped by CD modules with -100 and -300 ps/nm dispersion. The chirped optical pulses were captured by a realtime digitizer with bandwidth and sampling-rate of 16 GHz and 50 Gsample/s, respectively. Under these conditions, the spectral resolution is approximately 50 pm.