Discretely tunable optical delay based on wavelength multi-casting and dispersion

Abstract

We propose a low-power and low-cost tunable optical delay using wavelength multi-casting based on injection locking in Fabry-Pérot laser and dispersion. We achieve error-free operation at a maximum delay of 954 ps. IntroductionTunable all optical delay is a critical component for many telecommunication applications. Largest amounts of optical delay have been achieved using a technique based on wavelength conversion and dispersion; the delay is the product of dispersion parameter and the wavelength shift įȜ [1-3].Wavelength conversion schemes typically require high optical power, and therefore, high power amplifier stage [1-6]. The approaches based on semiconductor optical amplifier alleviate high power requirement but suffer from high noise figure [7]. In this paper, we use the conversion-dispersion method with a cost-effective and low-power wavelength conversion technique, i.e., injection locking in Fabry-Pérot laser (FPL) [8,9]. The incoming data stream is copied to multiple simultaneous channels by wavelength-multi-casting. The newly generated signals are sent to an FBG with 125 ps/nm dispersion. The signal with the desired delay is selected using optical filtering, and is then reconverted to its original wavelength. Both wavelength conversion and reconversion are performed in FPL. We emphasize that the desired delay is achieved only by selecting the corresponding wavelength and no further adjustments in the setup up are required. In our proof-of-concept demonstration, we use four channels and obtain four delays in multiples of 318 ps; continuous and fine tuning can be achieved by tuning the FBG. We show error free performance for the four channels at 2.5 Gb/s. The maximum operation bit rate is determined by the longitudinal mode spacing (determined by the cavity length) of the available FPL, 1.17 nm. A FPL with larger mode spacing can be used for wavelength conversion at higher data rates. For example, in [8] a FPL of 1.6 nm mode spacing was used for eight-channel wavelengthmulti-casting at 10 Gb/s.