M.R. Mokhtar

Wavelength tuning of fiber Bragg gratings over 90 nm using a simple tuning package

We demonstrate a silica-based tunable fiber Bragg grating filter with a wavelength tuning range over 90 nm. A bend-tuning technique in a simple tuning package is employed to obtain a wide wavelength tuning range from 1634 to 1544 nm, covering the entire L-band and a half of the C-band. The polarization-mode dispersion and polarization-dependent loss of the device show little variations over the whole operating region.

Reconfigurable multilevel phase-shift keying encoder-decoder for all-optical networks

We demonstrate the application of a uniform Bragg grating as a dynamically reconfigurable phase encoder-decoder for optical systems. Precise discrete phase modulation between chips is obtained simply by heating segments along the grating with fine resistive wires. Its reliability to generate and recognize various phase code sequences is demonstrated in a 16-chip 20-Gchip/s quaternary phase-shift keying coherent optical code-division multiple access experiment. The bit-error-rate response is also included to highlight its performance.

A 43-W C-band tunable narrow-linewidth erbium-ytterbium codoped large-core fiber laser

The authors report a widely tunable and highly efficient cladding-pumped erbium-ytterbium codoped large-core fiber laser, generating up to 43 W of output power at /spl sim/1.5 /spl mu/m with a narrow linewidth (0.16-nm full-width at half-maximum) and a good beam quality (M/sup 2/<1.7). By use of a tunable narrow-band fiber Bragg grating, the laser wavelength was tuned from 1532 to 1567 nm, limited upwards by the tuning range of the fiber grating. The overall slope efficiency was 32% with respect to launched pump power.

Improving signal quality in a spectrum-sliced WDM system using SOA-based noise reduction

We present an experimental and numerical study into the filtering effects in a spectrum-sliced incoherent light system incorporating a semiconductor optical amplifier (SOA) for noise reduction. Techniques to reduce the signal degradation caused by post-SOA filtering are investigated. The alignment of the receiver/demultiplexer filter relative to the input spectrum-slice is demonstrated to have a noticeable impact on the received signal quality. We also show that the linewidth enhancement factor /spl alpha/ of the SOA has a marked effect on the observed spectral distortion, which results in a strong dependence of the received signal quality on /spl alpha/. Our results illustrate the potential to improve system performance by optimized SOA design.

Rapidly reconfigurable optical phase encoder-decoders based on fiber Bragg gratings

We demonstrate the capacity for fast dynamic reconfiguration of optical code-division multiple access (OCDMA) phase en/decoders based on fiber Bragg gratings and a thermal phase-tuning technique. The tuning time between two different phase codes is measured to be less than 2 s. An OCDMA system using tunable-phase decoders is compared with a system using fixed-phase decoders and, although the system using fixed-phase decoders exhibits a shorter output autocorrelation pulsewidth and lower sidelobes, the system using tunable-phase decoders has advantages of flexibility and a more relaxed requirement on the input pulsewidth

Direct characterization of the spatial effective refractive index profile in Bragg gratings

We propose a pulse response method to directly characterize the phase of the spatial index modulation, including the dc refractive index distribution (distributed phase shift), discrete phase, and chirp of fiber Bragg gratings (FBGs). This method is based on the observation that the spatial phase of gratings is directly related to the temporal phase of its pulse response. Therefore, the phase of the spatial index modulation can be characterized directly by measuring the temporal phase of the pulse response of FBGs. This method is then used to characterize an FBG with a current-induced phase shift.

Simple dynamically reconfigurable OCDMA encoder/decoder based on a uniform fiber Bragg grating

We have demonstrated that a uniform fiber Bragg grating can be used in reconfigurable OCDMA phase-encoding/decoding applications by deploying fine heating elements at equal intervals along the fiber grating. One single fiber Bragg grating comprising the device, offers the advantages of compactness and low fabrication complexity, and we demonstrate its application in an 8-chip 20 Gchip/s bipolar configuration.

Reconfigurable all-optical packet switching based on fiber Bragg gratings

We report an all-optical bit-serial packet switched system which uses a fiber Bragg grating (FBG)-based reconfigurable device to recognize optical headers. The decoder is compatible with fixed SSFBG header encoders and has a reconfiguration time of < 2 s

Wideband compression-tuned all-fibre DFB laser: analysis and characterisation

The optical output from an all-fibre DFB-laser compression tuned over most of the C-band is analysed and characterised. The single-polarisation and line-width performance of the device is maintained across the full tuning range.

Rapidly reconfigurable phase code generation and recognition using fiber Bragg gratings

We demonstrate a 16-chip, 40 Gchip/s, reconfigurable fiber Bragg grating based quaternary phase en/decoder with a tuning time of <2s between two different phase codes