H. Y. Tam

Dissipative vector solitons in a dispersionmanaged cavity fiber laser with net positive cavity dispersion.

We report on the experimental observation of gain-guided vector solitons (GGVSs) in a dispersion-managed fiber laser mode-locked with a semiconductor saturable absorber mirror (SESAM). Both the frequency-locked and phase-locked GGVS were observed. In addition, formation of multiple GGVSs and GGVS harmonic mode-locking were also experimentally revealed. Numerical simulations confirmed the GGVS formation in the fiber lasers.

All-optical bit-error monitoring system using cascaded inverted wavelength converter and optical NOR gate

A novel all-optical bit-error monitoring system is demonstrated by cascading two all-optical logic gates: an inverted wavelength converter and an optical NOR gate which are realized using injection-locked laser diodes operating at different thresholds. Real-time optical monitoring signal is generated which indicates the positions and duration of both bit and burst errors in 10-Gb/s nonreturn-to-zero signals.

Stimulated soliton pulse formation and its mechanism in a passively mode-locked fibre soliton laser

We report on the stimulated formation of soliton pulses in a passively mode-locked fibre soliton laser. We found experimentally that if there are soliton pulses in the cavity, new soliton pulses can be generated one by one with very low pump threshold. We show that the mechanism for the soliton pulse generation is a soliton shaping of dispersive waves in the laser.

Tunable dual-wavelength-switching fiber grating laser

We report a tunable dual-wavelength-switching fiber grating laser by exploiting the large homogeneous gain broadening in erbium (Er)-doped fiber to suppress simultaneous lasing. Wavelength switching was accomplished through a novel design which has two overlapping cavities sharing a single-gain medium. The loss corresponding to one of the lasing wavelengths can be modulated via an optical chopper. Output power of about 6 mW and extinction ratio up to 50 dB were observed. The lasing wavelengths were tunable and switching was demonstrated for wavelength separations ranging from 0.35 to 23.5 nm.

Fusion Splicing Holey Fibers and Single-Mode Fibers: A Simple Method to Reduce Loss and Increase Strength

We demonstrate a novel method for low-loss splicing Ge-doped holey fibers (HF) with subwavelength core size and high numerical aperture fibers by using a conventional fusion splicer. We found that a large overlap distance of the fibers during fusion would decrease the splice loss and increase the splice strength. The lowest splice loss achieved for a fiber with a core diameter of 1.27 mu m and air-filling fraction of >0.95 was ~ 1 dB at 1550 nm, with a bend failure radius of 0.8 cm. With the same method, we also observed improvement in terms of loss and strength with larger core size HF.

Temperature-Insensitive Fiber Bragg Grating Based Tilt Sensor With Large Dynamic Range

We present a novel and simple temperature-insensitive fiber Bragg grating (FBG) based smart tilt sensor. The sensor design is free from any inherent mechanical joints/frictions with a capability to measure magnitude as well as the direction of the inclination. The first design is with a sensitivity of 0.00282 nm/° in a very large dynamic range of ± 35°. The sensor response is optimized against design parameters and observed to be completely reversible. Since there is a strain discrepancy on individual FBGs of the first design, a modified design is then proposed for optimization. An excellent sensitivity of 0.0395 nm/° , resolution of 0.013° and accuracy of 0.051° have been achieved. These features along with the freedom to tune the dynamic range, accuracy of measurement and the sensitivity of the proposed sensor to a desired operation range make the proposed sensor of extreme importance for practical engineering applications.

Reconfigurable Microwave Photonic Filter Using Multiwavelength Erbium-Doped Fiber Laser

A microwave photonic filter using a simple and novel multiwavelength erbium-doped fiber laser (EDFL) is proposed. The filter was experimentally demonstrated featuring tunability and reconfigurability by adjustment of the output from the EDFL. The experimental results show excellent agreement with the numerical simulations.

Simultaneous repolarization of two 10-Gb/s polarization-scrambled wavelength channels using a mutual-injection-locked laser diode

An all-optical polarizer, which can repolarize a highspeed data signal without converting the state-of-polarization variations into amplitude jitters, is realized using a mutual injection-locked laser diode. The all-optical polarizer is used to simultaneously realign the state-of-polarizations of two 10-Gb/s polarization-scrambled nonreturn to zero signals without state-of-polarization characterization and feedback control.

Vertical Displacement Measurements for Bridges Using Optical Fiber Sensors and CCD Cameras — A Preliminary Study

Bridge managers all over the world are always looking for simple ways to measure bridge vertical displacements for structural health monitoring. However, traditional methods to obtain such data are either tedious or expensive. There is a need to develop a simple, inexpensive, and yet practical method to measure bridge vertical displacements. This paper proposes two methods using either optical fiber (FBG) sensors or a charge-coupled-device (CCD) camera, respectively, for vertical displacement measurements of bridges. The FBG sensor method is based on the measured horizontal strains together with the identified curvature functions obtained by a self-developed FBG Tilt sensor. CCD cameras use a large number of pixels to form an image. The CCD camera method utilizes image processing techniques for pixel identification and subsequent edge detection. A preliminary study to validate the proposed methods in laboratory was presented. The tests include applying the methods to determine the vertical displacements separately for a concrete beam and a steel beam under various loadings. The comparisons include their installations, costs, degrees of accuracy, external factors affecting the measurement, etc. It was concluded that both methods could be used for vertical displacement measurement, and they could be complementary with one another. It was suggested to further improve the two methods developed and a successful outcome will not only help to solve an important problem for bridge management, but also prepare the way for better structural health monitoring techniques.

Multiwavelength laser source using linear optical amplifier

We propose and demonstrate a high-performance multiwavelength ring laser based on a linear optical amplifier (LOA) for potential applications in dense wavelength-division-multiplexing communication systems. Experimental results indicate that the inhomogeneous gain medium provided by the LOA reduces the gain competition and leads to stable multiwavelength lasing. Thirty-eight wavelengths covering C+L-band with 0.8-nm channel spacing are generated at room temperature. Simultaneous tuning of multiwavelengths is demonstrated and a stability test shows a power fluctuation of less than 0.2 dB during a 3-h test.