All-optical pulse reshaping and retiming systems incorporating pulse shaping fiber Bragg grating

Abstract

Abstract-This paper demonstrates two optical pulse retiming and reshaping systems incorporating superstructured fiber Bragg gratings (SSFBGs) as pulse shaping elements. A rectangular switching window is implemented to avoid conversion of the timing jitter on the original data pulses into pulse amplitude noise at the output of a nonlinear optical switch. In a first configuration, the rectangular pulse generator is used at the (low power) data input to a nonlinear optical loop mirror (NOLM) to perform retiming of an incident noisy data signal using a clean local clock signal to control the switch. In a second configuration, the authors further amplify the data signal and use it to switch a (low power) clean local clock signal. The S-shaped nonlinear characteristic of the NOLM results in this instance in a reduction of both timing and amplitude jitter on the data signal. The underlying technologies required for the implementation of this technique are such that an upgrade of the scheme for the regeneration of ultrahigh bit rate signals at data rates in excess of 320 Gb/s should be achievable.Index Terms-All-optical regeneration, fiber Bragg grating, nonlinear optical loop mirror, optical pulse shaping, ultrashort optical pulses.

Linear-distortion compensation using XPM with parabolic pulses

“…Pulses from a ~2 ps 10 GHz modelocked erbium fiber ring laser (MLL) operating at 1542 nm were first split into two paths using a 50:50 coupler. One path was wavelength-converted in a nonlinear optical loop mirror (NOLM), see for example [5] for further details, thus generating ~3 ps pulses at a wavelength of 1556 nm. These pulses were subsequently distorted using either GVD in a length of SMF or a severe linear distortion imposed by a fiber Bragg grating (FBG), thus forming the signal to be processed.…”

Compensation of Linear Distortions by Using XPM With Parabolic Pulses as a Time Lens

“…Pulses from a 2-ps 10-GHz mode-locked erbium fiber ring laser (MLL) operating at 1542 nm were first split into two paths using a 50 : 50 coupler. One path was wavelength-converted in a nonlinear optical loop mirror (NOLM), thus generating 3-ps pulses at a wavelength of 1556 nm [6]. These pulses were subsequently distorted using either secondorder dispersion [group-velocity dispersion (GVD)] in a length of single-mode fiber (SMF), or third-order distortion imposed by a fiber Bragg grating (FBG), to form the target signal to be processed.…”

All-optical 160 Gbit/s RZ data retiming system incorporating a pulse shaping fibre Bragg grating

“…This provides optimal resilience to timing jitter-induced errors, and also reduces the absolute accuracy for temporal bit alignment. In the technique that we present in this paper, we achieve timing jitter reduction in transmission systems operating at data rates up to 160 Gbit/s by linearly reshaping RZ data pulses into longer rectangular (flat-top) pulses and then switching these pulses in a nonlinear Kerr switch with a synchronous optical clock signal [3,4]. The required pulse shaping is performed using Superstructured Fibre Bragg Grating (SSFBG) technology, which allows the implementation of optical filters with accurately controlled frequency and phase responses of almost arbitrary complexity in a single continuous grating structure [5].…”

“…Shaping of a pulse with a pre-known spectrum can be achieved by feeding it into a SSFBG which has been designed so that the reflected spectrum has the amplitude and phase characteristics of the desired waveform. Using this linear technique, we have previously demonstrated the reshaping of short pulses of a few picoseconds duration into rectangular pulses of different pulse widths (10-20ps) [4][5][6]. However, this extremely versatile technique is suitable for other shaping applications as well.…”