All-optical NRZ-to-PRZ format transformer with an injection-locked Fabry-Perot laser diode at unlasing condition

Abstract

By using an optical nonreturn-to-zero (NRZ) format data-stream to injection-lock an synchronously modulated Fabry-Perot laser diode at below threshold condition (without DC driving current), an output data-stream with pseudo-return-to-zero (PRZ) format can be generated at bit rate of up to 2.488 Gbit/s. Such an NRZ-to-PRZ format transformation is due to the injectionlocking induced gain-switching of the FPLD with the incoming NRZ data. The PRZ data-stream with a maximum on/off extinction ratio of 12.2 dB is obtained under the optical injecting power of -2 dBm and the RF driving power of 24.4 dBm. The best side-mode suppression ratio of 40 dB and the lowest timing jitter of 0.4 ps for the PRZ data-stream are observed. A power penalty of 1.2 dB is measured at a bit-error rate of 10-9 after NRZ-to-PRZ transformation. In application, the demonstration of an all-optical OR logic gate using the FPLD-based NRZ-to-PRZ transformer is also reported.

Beyond-Bandwidth Electrical Pulse Modulation of a TO-Can Packaged VCSEL for 10 Gbit/s Injection-Locked NRZ-to-RZ Transmission

“…The following derivation has been modified to agree, after some simplifications, with the solution given in the tutorial. First of all, the injection-power-dependent threshold current of the VCSEL can be expressed as [4] (1) where and denote the respective threshold currents of the VCSEL without and with external optical injection, the electron charge, the volume of the active region, and the photon lifetime and carrier lifetime, respectively, the gain that varies linearly with the carrier density of newton per cubic centimeter, the spontaneous emission rate (expressed by with referred to as the spontaneous emission factor), the group velocity, the photon number injected into the laser cavity, the maximum photon number in the injection-locked mode, the linewidth enhancement factor, and the coupling coefficient. The external injection essentially reduces the threshold of the VCSEL due to the increasing number of photons injected into the laser cavity.…”

“…10 and 11). In the meantime, the linewidth of the VCSEL output [26] should also be modified as (4), shown at the bottom of the page, where is the linewidth enhancement factor with and denoting the real and imaginary parts of the refractive index and and denoting the small index and optical gain variations under the variation of the carrier density by external injection. Equations (3) and (4) reveal that the enlarged chirp and the broadened linewidth are straightforward consequences of the RZ data stream generated from the gain-switched VCSEL under externally NRZ injection-locked conditions.…”

“…Numerous scenarios have been proposed to demonstrate RZ generation and NRZ-to-RZ conversion, with simplified all-optical schemes persistently emerging during the past decade. By using a directly gain-modulated and single-(or dual-) wavelength injection-locked Fabry-Perot laser diode (FPLD), the NRZ-to-RZ data format conversion can only be performed at low bit rates ( Gbit/s) [3], [4]. Some of the 10 Gbit/s "all-optical" NRZ-to-RZ converters have been demonstrated by using semiconductor optical amplifiers (SOAs) and/or loop mirrors under a self-or cross-phase modulation scheme [5]- [7].…”

Nonlinear Photonic Signal Processing Subsystems and Applications

“…Although the injection locking of semiconductor laser has been studied for two decades, new aspects and applications have only become apparent with recent advances in fiber optic technology. Recently, injection locked lasers have been used for different kinds of nonlinear photonic signal processing, including signal regeneration (Weich et al, 1994, Kakagawa et al, 2001, Inoue & Oda, 1995, Yamashita & Suzuki, 2004, Kuramoto & Yamashita, 2003, optical repolarization , optical packet demultiplexing (Chan et al, 2003), modulation format conversion , Chang et al, 2004). Injection locking also shows promising applications in optical packet switched networks , Cable-TV networks , passive optical networks (PONs) ) and radioover-fiber (ROF) networks (Lu et al, 2008).…”

All optical format conversion at 10 Gbps using SOA and optical band-pass filter

“…So far, reports have been presented on all-optical format conversions between RZ and NRZ using different techniques. Recently, various demonstrated schemes have been proposed to realize NRZto-RZ format conversion, such as using an injection-locked Fabry-Pe´rot laser diode [7,8], using the nonlinearity of a semiconductor optical amplifier (SOA) [9,10], using nonlinearity of an optical fiber [11], using SOA assisted by an optical band-pass filter and using a SOA loop mirror [4,11,12]. The reported injection locking technologies were with low bit rate due to the directly modulated source.…”