Minghuang Sang

All-fiber birefringent filter with fine tunability and changeable spacing

A novel all-fiber birefringent filter has been proposed and demonstrated. Simulation results show that the birefringence fiber filter with one section of polarization-maintenance fiber (PMF) can be finely tuned with its free spectrum range, and the filter with two sections of PMFs can generate changeable wave-length spacing. Experiment agrees well with simulation. This filter has potential applications for flexible multiwavelength fiber laser.

Nonlinear-polarization-rotation based multiwavelength erbium-doped fiber lasers with highly nonlinear fiber

A multiwavelength erbium-doped fiber laser based on nonlinear polarization rotation with incorporation of a highly nonlinear fiber has been demonstrated. Stable multi-wavelength operation at room temperature is realized owing to the intensity-dependent transmission in fiber laser with nonlinear-polarization-rotation effect. And benefiting from the four-wave mixing in the highly nonlinear fiber, the uniformity and stabilization of the output multi-wavelength lasing have been greatly improved, in comparison with similar laser using single-mode fiber. Moreover, the wavelength spacing can be arbitrarily chosen according to the requirement through changing the PMF length.

Wavelength-spacing switchable multiwavelength fiber lasers based on nonlinear polarization rotation with cascaded birefringence fibers

A wavelength-spacing switchable multiwavelength erbium-doped fiber lasers incorporating a highly nonlinear fiber (HNLF) based on nonlinear polarization rotation (NPR) has been demonstrated. The intensity-dependent transmission effect originating from NPR ensures room-temperature multi-wavelength lasing, which is further self-stabilized by the four-wave mixing in the HNF. Moreover, the equivalent Lyot birefringence fiber filter with two cascaded birefringence fibers makes the wavelength spacing switchable depending on the effective length of the birefringence fiber. The experimentally obtained multiwavelength outputs agree well with the simulation filter transmission spectra.

Switchable multiwavelength erbium-doped fiber laser with cascaded fiber Bragg gratings and dual-section Lyot–Sagnac filter

We propose and demonstrate a novel switchable multiwavelength erbium-doped fiber laser with a overlapping linear cavity, which is formed by a dual-section Lyot–Sagnac filter and three fiber Bragg gratings (FBGs). Taking advantage of the high extinction of the Lyot–Sagnac filter, independent controlling of the different wavelength losses and the spatial hole burning in the overlapping linear cavities, with this structure we realize stable switchable multiwavelength laser emission at room temperature. An output signal to background noise ratio of ∼43 dB and less than 3 dB fluctuation on output power were observed for all wavelength switching cases.

All-optical wavelength conversion based on cross-phase modulation

We have proposed and demonstrated an all-optical scheme of wavelength conversion based on cross-phase modulation (XPM). The frequency shift and broadening of a continuum wave induced by XPM in a dispersion-shifted fiber (DSF) is experimentally observed. Then, the wavelength conversion is achieved through the filtering by a fiber grating. The results indicate that wavelength conversion based on the cross-phase modulation of DSF is simple, efficient, and universal with wide conversion ranges and high rates.

Gain characteristic of a dual-pump fiber-optical parametric amplifier with a highly nonlinear fiber

The gain characteristic of a dual-pump fiber-optical parametric amplifier with a highly nonlinear fiber is demonstrated. The influence of various parameters on the gain spectrum of the dual-pump fiber-optical parametric amplifier is numerically simulated. The results indicate that broadband and flat gain can be obtained under optimized parameters.

Multiwavelength emission and passive mode-locking from a same fiber laser with nonlinear optical loop mirror

Fiber laser with two polarization-dependent output states is demonstrated. On one hand, nonlinear polarization rotation induced intensity-dependent loss of nonlinear optical loop mirror can balance mode competition of homogenous broadening gain medium, and thus allows for stable room-temperature multiwavelength generation. On the other hand, intensity-dependent transmission can act as an equivalent saturable absorber, which results in passively mode-locking of fiber laser. It may be a potential multifunction fiber laser.

Multiwavelength fiber laser based on nonlinear polarization rotation

Multiwavelength fiber laser is a perfect light source for future wavelength-division-multiplexing optical communication systems. A multiwavelength fiber laser based on nonlinear polarization rotation with up to 18 wavelengths has been proposed and demonstrated. The intensity- and wavelength-dependent loss induced by nonlinear polarization rotation effect is used to alleviate the mode competition in the homogeneous broadening gain medium of erbium-doped fiber. Instead of traditional filters, a polarization-maintaining fiber is inserted into the laser cavity, with which the polarization-dependent isolator composes an equivalent Lyot birefringent fiber filter. The in-line birefringence fiber filter is used to simplify the laser configuration, which benefits systematic integration. The effect of the 980 nm pump power on the multiwavelength generation is investigated. It is shown that the pump power contributes a lot to the evenness of the multiwavelength spectra due to the intensity dependence of nonlinear polarization rotation effect.