W.H. Loh

Stable single-frequency traveling-wave fiber loop laser with integral saturable-absorber-based tracking narrow-band filter.

We demonstrate stable single-frequency and polarization operation of a traveling-wave, Er(3+)-doped fiber loop laser by incorporating an unpumped Er(+3)-doped fiber section butted against a narrow-band feedback reflector. The saturable absorber acts as a narrow bandpass filter that automatically tracks the lasing wavelength, thus ensuring single-frequency operation. Output powers up to 6.2 mW at 1535 nm were obtained for launched pump powers of 175 mW at 1064 nm. At this output, the relative intensity noise was less than -112 dBy/Hz at frequencies above 200 kHz and a laser linewidth of less than 0.95 kHz, whereas the lasing frequency was observed to drift slowly (~170 MHz/h) because of environmental effects.

Triple-frequency operation of an Er-doped twincore fiber loop laser

Simultaneous laser operation of three single-frequency modes from an inhomogeneously broadened Er-doped twincore fiber loop laser is reported. Equal output power of 390 /spl mu/W, separation 0.5 nm, and linewidth <10 kHz were measured for each mode in a travelling wave cavity comprising a single gain medium. In addition up to eight wavelength operation has been observed, demonstrating that twincore EDFAs can provide channel equalization in an eight-channel multiamplifier optical network.

COMPLEX GRATING STRUCTURES WITH UNIFORM PHASE MASKS BASED ON THE MOVING FIBER-SCANNING BEAM TECHNIQUE

We present experimental results of complex grating structures fabricated with uniform phase masks by the moving fiber-scanning beam approach. Pure apodized gratings with side-mode-suppression levels in excess of 40 dB, self-apodized linearly chirped gratings, and phase shifted gratings with narrow-band transmission peaks have all been realized.

Efficient single-frequency fiber lasers with novel photosensitive Er/Yb optical fibers

Boron- and germanium-doped highly photosensitive cladding is used in a novel design to achieve photosensitive Er/Yb-doped fibers, permitting short, strong gratings (length approximately 1 cm, reflectivity >99%) to be written without hydrogenation. The high absorption at 980 nm in Er/Yb fibers permits efficient pump absorption over a short device length, which is ideal for achieving highly efficient single-frequency fiber lasers. Both single-frequency Bragg-grating reflector and distributed-feedback lasers with slope efficiencies of 25% with respect to launched pump power have been realized in such fibers.

Polarimetric Er(3+)-doped fiber distributed-feedback laser sensor for differential pressure and force measurements.

We propose and demonstrate a polarimetric Er(3+) -doped fiber distributed-feedback laser sensor in which a force applied transversely along the fiber laser induces a birefringence that gives rise to a change in the beat frequency between the two orthogonally polarized laser modes. We measure a sensitivity of ~9.6 GHzysNymmd, a wide dynamic range with stable two-mode operation for frequency separations up to 50 GHz, and high sensor resolution owing to the narrow beat frequency bandwidth of <10 kHz. The temperature sensitivity is dominated by the temperature dependence of the inherent birefringence, which was measured to be -130 kHz/ degrees C. The sensor permits independent pressure-force and temperature measurements.

Dispersion compensation over distances in excess of 500 km for 10-Gb/s systems using chirped fiber gratings

We report on results of a system trial involving dispersion compensating chirped fiber gratings, demonstrating that transmission up to 537 km of standard telecommunications fiber is now feasible at 10 Gb/s, with a pair of 10-cm-long gratings cascaded together.

Increased amplifier spacing in a soliton system with quantum-well saturable absorbers and spectral filtering

The spacing between optical amplifiers in a long-haul soliton system may be increased to 100 km by using only passive quantum-well saturable absorbers and narrow-band filters for soliton control. After transmission over 9000 km at 10 Gbits/s, the effects of soliton-soliton interaction and Gordon-Haus jitter in the proposed systemyield bit error rates of better than 10(-9).

Towards efficient and broadband four-wave-mixing using short-length dispersion tailored lead silicate holey fibers

We demonstrate four-wave-mixing based wavelength conversion at 1.55 mum in a 2.2 m-long dispersion-shifted lead-silicate holey fiber. For a pump peak power of ~6 W, a conversion efficiency of -6 dB is achieved over a 3-dB bandwidth of ~30 nm. Numerical simulations are used to predict the performance of the fiber for different experimental conditions and to address the potential of dispersion-tailored lead silicate holey fibers in wavelength conversion applications utilizing four-wave-mixing. It is shown that highly efficient and broadband wavelength conversion, covering the entire C-band, can be achieved for such fibers at reasonable optical pump powers and for fiber lengths as short as ~2 m.

Single frequency erbium fiber external cavity semiconductor laser

A novel external cavity configuration for stable single frequency operation of the semiconductor laser is demonstrated. By using an erbium doped fiber as the external cavity, longitudinal mode-hopping is suppressed, ensuring single frequency operation. Employing a 3m long fiber cavity, resolution-limited optical linewidths of a kHz are obtained.

Suppression of self-pulsing behavior in erbium-doped fiber lasers with resonant pumping: experimental results

Experimental results are presented showing that resonant pumping can significantly improve the stability of erbium-doped fiber lasers. In particular, it is observed that an erbium fiber laser that exhibits sustained spiking behavior when pumped at 980 nm will revert to stable cw operation when pumped at 1510 nm.