Paul S. Westbrook

Measurement of residual chromatic dispersion of a 40-Gb/s RZ signal via spectral broadening

In this letter, we examine the spectrum of a 40-Gb/s return-to-zero (RZ) data stream, which has been broadened by self-phase modulation in a nonlinear fiber. Spectra were recorded as the residual chromatic dispersion at the input of the nonlinear fiber was varied using a tunable dispersion element. We show that spectral broadening can provide a useful measure of the residual chromatic dispersion of the data stream.

Holographic methods for phase mask and fiber grating fabrication and characterization

The fiber grating fabrication based on use of the phase masks is the most stable and accurate manufacturing technology. This paper presents a brief overview of holographic methods of phase masks and fiber Bragg gratings (FBGs) writing and characterization with emphasis on the chirped gratings. We discuss the range of FBG parameters enabled by current technological methods, as well as the relation between the accuracy of FBG parameters and the performance of FBG-based dispersion compensators. While holographic phase mask and FBG writing principles have much in common, the phase mask and FBG production is a unified technology where the quality of the FBG is determined by numerous factors in the process of fabrication. As one of the significant factors, we study the effect of mirror non-flatness on the group delay ripple of chirped FBG. The quality of phase masks and FBGs is often important to characterize directly. In this paper we consider holographic side-diffraction methods of their characterization, which are very accurate and provide the information that is not simple to obtain from spectroscopic measurements.

Interferometric characterization of phase masks

We demonstrate a novel interferometric technique for highly accurate characterization of phase masks used in optical fiber grating fabrication. The principle of the measurement scheme is based on the analysis of the interference pattern formed between the first- and zero-order beams transmitted through or reflected from the grating under test. For spatial resolution of a few millimeters, our methods allow the determination of local variations of the order of 1-microm grating period with an accuracy of a few picometers. These methods are applicable to a broad class of diffractive grating structures.

Simulation of two-photon absorption in Raman DFB lasers

We present an efficient split-step solver for the nonlinear coupled mode equations with two-photon absorption to investigate the feasibility of Raman DFB lasers in highly nonlinear materials such as chalcogenide glasses.

A seven core fiber DFB

We demonstrate fiber DFB lasers in a seven core Er doped fiber. DFB grating cavities were fabricated in all cores at once via a single UV exposure. Lasing was observed in all seven cores.

Light Reflection of Broadband Nonlinear Optical Pulses in Narrowband Fiber Bragg Gratings

We compute nonlinear light reflection from fiber gratings using the coupled mode equations and an undepleted pump approximation. Our simulations show features similar to measurements of light reflection from fiber Bragg gratings during continuum generation.

Analysis of 25+ Meter Long Continuous Distributed Sensor Grating Arrays

An automated analysis of long arrays of distributed sensor gratings in twisted multicore fiber is presented. As an example, we analyze 7×744 quasi-continuous gratings from a single OFDR measurement written through UV transparent coating.

Highly Efficient Distributed Feedback Brillouin Fiber Laser

An efficient single frequency distributed feedback (DFB) Brillouin fiber laser producing 22mW of Stokes output, using 81mW of pump from a semiconductor DFB laser, is shown. The laser operated for a pump frequency detuning >1GHz.

High-power single-mode all-fiber femtosecond laser system and its use in continuum generation

We present a source of high power femtosecond pulses at 1550 nm generating compressed pulses at the end of a single mode fiber pigtail. The system generates sub 35 femtosecond pulses at a repetition rate of 50 MHz, with average powers greater than 400 mW. The pulses are generated in a passively modelocked, erbium doped fiber laser, and amplified in a short, erbium doped amplifier. The output of the fiber amplifier consists of highly chirped picosecond pulses. These picosecond pulses are then compressed in standard single mode fiber. While the compressed pulses in the SMF pigtail do show a low pedestal that could be avoided with the use of bulk-optic compression the desire to compress the pulses in SMF is motivated by the ability to splice the single mode fiber to a nonlinear fiber, for continuum generation applications. We demonstrate that with highly nonlinear dispersion shifted fiber (HNLF) fusion spliced directly to the amplifier output, we generate a supercontinuum spectrum that spans more than an octave, with an average power 350 mW. Such a high power, all-fiber supercontinuum source has many important applications including frequency metrology and biomedical imaging.

Application of adiabatic UV correction to multi-channel chirped fiber gratings

We demonstrate reduction of group delay ripple from 24 ps to 5 ps peak to peak in a multichannel chirped fiber grating by adiabatic UV post processing.