R. Kashyap

Laser-trimmed four-port bandpass filter fabricated in single-mode photosensitive Ge-doped planar waveguide

A single-mode photosensitive waveguide Mach-Zehnder interferometer fabricated in Ge-doped planar silica is reported. Two-millimeter-long identical-wavelength reflection gratings using external UV beams have been written into each arm to demonstrate a four-port bandpass device for the first time using this technology. The imbalance in the arms after writing of the gratings is compensated by laser trimming of one photosensitive arm of the interferometer. A 96.8% reflection of the output port is measured, and 58.8% of the total power available at the input at 1.5558 mu m in the bandpass of 1 nm is transmitted at the second input port after laser trimming. The total fiber-to-fiber insertion loss of the device is measured to be 1.35 dB.<<ETX>>

Duration-tunable 0.2-20-ps 10-GHz source of transform-limited optical pulses based on an electroabsorption modulator

A 10-GHz source of pulse-width-tunable bandwidth-limited optical pulses operating near 1.55 μm based on an electroabsorption modulator and a tunable-dispersion chirped fiber Bragg grating is described both experimentally and theoretically. The pulse-width range attainable from this device is significantly extended through the exploitation of nonlinear adiabatic solitonlike pulse compression and spectral filtering.

All-fiber dispersive transmission filters based on fiber grating reflectors

A novel, low-insertion-loss transmission f ilter with the implementation of linearly chirped fiber Bragg grating reflectors and polarization-splitting fiber fusion couplers is reported. Pulse chirping, chromatic dispersion compensation, and pulse compression are demonstrated. Cascading of dispersive filters, including application to a low-loss pulse stretchery/recompressor of femtosecond pulses, is also demonstrated.

Ultraviolet absorption studies on photosensitive germanosilicate preforms and fibers

Detailed measurements of the ultraviolet absorption spectra of germanosilicate preforms, multimode and single‐mode fibers are presented. Significant differences between the spectra of preforms and fibers are revealed and these differences are thought to be caused by the stresses induced during fiber pulling. Measurements are also presented of the changes in the absorption spectra in single‐mode fibers into which reflection gratings have been written using an ultraviolet laser. These results suggest that changes in the absorption between 200 and 600 nm are not responsible for the inferred changes in the refractive index.

Multi Gbit/s bit parallel WDM transmission using dispersion managed fibers

This paper demonstrates the feasibility of a bit parallel WDM (BP-WDM) system using dispersion managed fibers. An expression for the total bit skew as a function of the fiber dispersion and system bandwidth is derived and compared with experimental results. A 4 bit/spl times/10 Gbit/s-per bit BP-WDM transmission experiment over 30 km DMF is used and an aggregate bite rate/spl times/distance product of 1.2 Tbit/s-km is obtained. The total bit skew of the system is reduced to one half of the bit period. We believe that systems using BPWDM will be useful for computer interconnects in high-speed parallel systems and ring networks.

Use of dispersion managed fibers in parallel WDM systems

The problem of serial electronic bottleneck in optical systems can be solved using parallel transmission. In these systems, there is no need for serial-to-parallel, and parallel-to-serial conversion since all bits in a digital word are transmitted simultaneously. Several parallel systems have been proposed in the literature and some of them are already commercially available. In this paper, the feasibility of a novel parallel WDM system using Dispersion Managed Fibers (DMF) is proposed. 10 GWord/s over 40 km of DMF at an aggregate bit rate-distance product of 160 Gbit/s/spl times/40-km is studied.