Shenping Li

A novel tunable all-optical incoherent negative-tap fiber-optic transversal filter based on a DFB laser diode and fiber Bragg gratings

We demonstrate experimentally a novel and simple tunable all-optical incoherent negative-tap fiber-optic transversal filter based on a distribution feedback laser diode and high reflection fiber Bragg gratings (FBGs). In this filter, variable time delay is provided by cascaded high reflection fiber Bragg gratings (FBGs), and the tuning of the filter is realized by tuning different FBG to match the fixed carrier wavelength, or adjusting the carrier wavelength to fit different FBG. The incoherent negative tapping is realized by using the carrier depletion effect in a distribution feedback laser diode.

Gain flattening of an erbium-doped fiber amplifier using a high-birefringence fiber loop mirror

We propose a flexible method for flattening the gain profile of an erbium-doped fiber amplifier (EDFA). The method is based on a high-birefringence fiber loop mirror (HiBi-FLM), which contains a number of high-birefringence fiber sections and polarization controllers. We show that, by setting the polarization controllers properly, the reflection spectrum of the loop mirror can be adjusted to compensate for the variations in the gain profile of the EDFA. The method is demonstrated experimentally by using a single-section HiBi-FLM and a two-section HiBi-FLM, respectively, With a two-section HiBi-FLM, we are able to flatten the gain profile of an EDFA to within /spl plusmn/0.9 dB over a bandwidth of 33 nm at the center wavelength of 1543 nm, under different operating conditions of the EDFA.

Self-seeding of Fabry-Perot laser diode for generating wavelength-tunable chirp-compensated single-mode pulses with high-sidemode suppression ratio

We report an effective technique for generating wavelength-tunable chirp-compensated single-mode pulses with a high sidemode suppression ratio (SMSR) based on self-seeding a Fabry-Perot laser diode. This technique relies on the use of a tunable linearly-chirped fiber Bragg grating to provide wavelength-selective feedback, output filtering, and chirp compensation. With this technique, we have generated chirp-compensated picosecond pulses with a SMSR higher than 40 dB over a tuning range of 11.5 nm.

Wavelength switching of semiconductor laser pulses by self-seeding from a chirped fiber Bragg grating

Wavelength switching of four wavelengths spanning 5.1 nm was realized by gain switching and self-seeding of a commercial Fabry-Perot (F-P) laser diode with a single in-fiber linearly chirped Bragg grating as the external cavity. A driving frequency up to 2 GHz was used and single mode operation with a side mode suppression ratio of 10 dB overall and 25 dB at best was achieved.

Fast accurate wavelength switching of an erbium-doped fiber laser with a Fabry–Perot semiconductor filter and fiber Bragg gratings

We propose a simple passive method for achieving fast accurate wavelength switching in an erbium-doped fiber laser. The method relies on a laser cavity formed with a Fabry–Perot semiconductor filter (FPSF) and narrow-band fiber Bragg gratings (FBGs), where the FBGs set the wavelength references and the FPSF can be tuned by changing its injection current to select a particular wavelength from those set by the FBGs. Because of the nonlinearity in the FPSF, optical negative feedback can be built up in the laser to suppress relaxation oscillations caused by wavelength switching. With this method, a wavelength switching time of less than 25 μs has been achieved experimentally.

Dynamic gain flattening of an erbium-doped fiber amplifier using a high-birefringence fiber loop mirror

A flexible method based on a high-birefringence fiber loop mirror is proposed for the gain flattening of an erbium-doped fiber amplifier. The gain profile was flattened to within /spl plusmn/0.9 dB over a 33 nm bandwidth.

Accurate fast wavelength switching of an erbium-doped fiber laser with a Fabry-Perot semiconductor filter

We have demonstrated a simple passive method for realizing fast accurate wavelength switching in a fiber laser. We have shown that the optical nonlinearity in the Fabry-Perot semiconductor filter can suppress relaxation oscillations effectively and stabilize the laser output. A clean wavelength switching in less than 25 /spl mu/s has been achieved.

Generation of wavelength-tunable chirp-compensated single-mode pulses with high sidemode suppression ratio from a self-seeded Fabry-Perot laser diode

We have demonstrated a simple and robust self-seeding scheme based on a linearly chirped Bragg fiber grating for the generation of wavelength-tunable short pulses with a high side mode suppression ratio (SMSR) and chirp compensation. Using this scheme, we have generated chirp-reduced single-mode gigahertz picosecond pulses with a wavelength-tuning range of 11.5 nm and a SMSR better than 40 dB over the entire tuning range.

Fabrication of long-period waveguide gratings

Long period gratings (LPGs) are fabricated on an ion- exchanged waveguide by the use of direct UV writing. The transmission spectrum of this LPG waveguide is analyzed. An attenuation of 22dB is observed at 1.55 micrometers .