A highly flexible optical packet compressor is presented. The compressor is capable of providing various compression ratios using the same hardware. It is composed of three parts: a chirped packet generator, a signal compressor, and a wavelength converter. In the chirped packet generator, the modulator intensity-modulates a series of supercontinuum chirped optical carriers and generates a series of chirped optical packets. The signal compressor compresses the chirped packets. The wavelength converter then transforms the compressed wideband optical packets into single-wavelength signals. We numerically demonstrate that using dispersive devices (chirped Bragg grating array or dispersion compensation fiber), we can compress both the width of pulses and the distance among pulses at the same time. This results in an increase of the bit rate. We also show that during the compression, the optical packet suffers distortion in the time domain, which can be defined as an extinction ratio. The distortion can be minimized by control parameters such as carrier chirping and modulating bandwidth. We present a highly flexible optical packet compressor, which is capable of compressing hundreds of bits packets from low speed (mega- or gigabits per second) to very high speed (up to 40 Gbits/s).
Wireless technology is a cost-effective means to bring broadband communications to both mobile users and home consumers; however, deploying next generation, multi-GHz wireless systems is currently too expensive. For these systems, photonic technologies can bring cost reduction as well as an increase in performance, mainly due to the ultra low-loss property of optical fibers. One approach to signal distribution is to capitalise on the vast fibre-optic distribution networks deployed within and between cities. A microwave carrier can be optically deployed from central offices to remote antenna sites using these optical links. This paper will discuss the generation of such a microwave carrier using a dual-wavelength, external-cavity laser (ECL).
Two different dual-wavelength ECL's, constructed with fiber-Bragg-gratings (FBG's), have been investigated. One uses a semiconductor gain chip with a dual-FBG acting as an external reflector. The other uses two similar dual-FBG reflectors on each side of a semiconductor optical amplifier (SOA). In both cases the wavelength separation between the gratings is 0.25 nm.
We will demonstrate that a dual-wavelength emission can be temporarily stabilized in the gain-chip ECL if a specific phase relation, between the external feedback from the FBG's and the residual feedback from the gain chip, is satisfied at both lasing wavelengths. The power of the RF beat signal generated by the dual-wavelength optical signal was typically 25 dB above the noise floor. The 3-dB linewidth of the RF signal was approximately 2 MHz and it can be tuned over a frequency range of 200 MHz. The physical mechanisms underlying the observed laser instability will be briefly discussed.