Qinghao Ye

Tunable multiwavelength Brillouin-erbium fiber laser with a polarization-maintaining fiber Sagnac loop filter

We demonstrate the generation of 12-wavelength comb with 14.5-nm tunable range in the Brillouin-Erbium fiber laser. This is achieved through tuning the gain profile of Erbium-doped fiber by a Sagnac loop filter with 18-cm polarization-maintaining fiber, in conjunction with modifying the wavelength of Brillouin pump. The experiment also demonstrates that the tunable range is closely equal to the 3-dB bandwidth of Sagnac loop filter due to its periodic transmission profile. Meanwhile, the effect of the 980-nm pump on the tunable multiwavelength generation is investigated. The power of 980-nm pump has a great effect on the wavelength number and the output power of the generated multiwavelength comb, but little on the tunable range. This technique may be applicable to multiwavelength operation lasers with a large tunable range.

Self-seeded multiwavelength Brillouin-erbium fiber laser.

We propose and demonstrate a self-seeded multiwavelength Brillouin-erbium fiber laser with an internally self-excited Brillouin pump, which is achieved by incorporation of a length of single-mode fiber together with a Sagnac loop mirror into a fiber ring cavity. In this simple scheme the Brillouin pump is self-excited in the fiber ring cavity and then used to seed the Brillouin multiwavelength comb in the single-mode fiber. Stable generation of more than 120 Brillouin Stokes wavelengths with relatively uniform amplitudes is demonstrated with this scheme. It is also shown that such a self-seeded Brillouin laser has good stability and repeatability.

Improvement of gain and noise figure in double-pass L-band EDFA by incorporating a fiber Bragg grating

An obvious improvement on both the gain and noise figure (NF) is demonstrated in the new double-pass L-band erbium-doped fiber amplifier (EDFA) with incorporating a fiber Bragg grating (FBG). Compared with the conventional L-band EDFAs, the gain is improved by about 6 dB in the new configuration for a 1580-nm signal with an input power of -30 dBm at 60 mW of 980-nm pump power. It is important that the NF is greatly reduced in the new configuration, as the FBG greatly compresses the backward amplified spontaneous emission. For the economical utility of pump power and erbium-doped fiber length, such a configuration may be a very competitive candidate in the practical applications of L-band EDFAs.

Gain-clamped erbium-doped fiber-ring lasing amplifier with low noise figure by using an interleaver

A novel all-optical gain-clamped erbium-doped fiber-ring lasing amplifier (GC-EDFRLA) has been demonstrated, in which the odd port of a 100/200-G interleaver was used to form a fiber-ring cavity to produce lasing oscillation for locking the gain and its even port was employed to export the amplified signals. In such a way, the problem existing in the conventional GC-EDFRLA is solved. The signal can be exported separately without the lasing power while the noise figure (NF) is very low. Finally, the GC-EDFRLA with a low NF of 4.2 dB was achieved.

Low noise-figure gain-clamped L-band double-pass erbium-doped fiber ring lasing amplifier with an interleaver

A new design of all-optical gain-clamped L-band double-pass (DP) erbium-doped fiber amplifier (EDFA) has been proposed and demonstrated, in which the input port and the odd-channel output port of an interleaver are connected with the DP configuration EDF through a circulator to form lasing ring cavity for clamping gain, and the even port is utilized to export the amplified signals. The low noise figure can be achieved because the lasing power copropagates with the signals, and it is exported separately from the amplified signal thanks to interleaver. Meanwhile, the fiber Bragg grating incorporated in DP configuration suppresses the backward amplified spontaneous emission generation, and therefore improves efficiently the gain and lowers the noise figure. In such a way, the clamped gain of 16.3 dB with a variation below 0.2 dB and noise figure below 5 dB are achieved in the new L-band all-optical gain-clamped EDFA.

Arbitrary numerator rational-harmonic mode locking in fiber ring lasers

Pulse generation with an arbitrary numerator is experimentally demonstrated in seventh- and ninth-order rational-harmonic mode-locked fiber lasers. Conventionally, the numerator of rational-harmonic mode locking is equal to 1. Furthermore, the experimental generation of the numerator m=5, 22nd-order rational-harmonic mode-locked pulse confirms that the amplitude distributions in such pulse trains are strongly modulated by the numerator m=1 lower-order rational-harmonic mode locking. The result is important, as it indicates that a higher-repetition-rate pulse train can be obtained by an arbitrary numerator rational-harmonic mode-locking technique.

Tunable gain-clamped double-pass erbium-doped fiber amplifier with a DBR lasing cavity including a fiber Bragg grating and a fiber reflection mirror

A tunable, gain-clamped (GC) double-pass Erbium-doped fiber amplifier (EDFA) using only one fiber Bragg grating (FBG) has been demonstrated, which solves the problem existing the conventional GC-EDFA using two FBGs, in which the clamped-gain is very difficult to be tuned. In the new GC-EDFA, the lasing oscillation for clamping the gain is produced between a FBG and a fiber reflection mirror, and a variable optical attenuator (VOA) is used to change the loss of the laser, which is filtered solely from a narrowband filter for tuning the clamped-gain, however it does not change the signal power directly. Meanwhile, the double-pass configuration enhances efficiently the gain, therefore, compared with the single-pass configuration, the maximum possible input signal power for gain-clamping is greatly extended. Furthermore, the FBG can depress the strong backward amplification spontaneous emission in double-pass configuration, so it can reduce the noise figure a certain extent. Finally, a gain-tunable GC-EDFA with a wide dynamic input power range is demonstrated.

Low-noise-figure gain-clamped L-band double-pass erbium-doped fiber ring lasing amplifier with an interleaver

A new design of all-optical gain-clamped L-band double-pass (DP) erbium-doped fiber amplifier (EDFA) has been demonstrated, in which, the input port and the odd-channel output port of interleaver are connected with a DP configuration EDF through a circulator to form lasing ring cavity for clamping gain, and the even port is utilized to export the amplified signals. A low NF can be achieved because the lasing co-propagates with the signal, and the lasing is exported separately from the amplified signal thanks to interleaver. Meanwhile, the fiber Bragg grating incorporated in DP configuration suppresses the backward ASE generation, and therefore improves efficiently the gain and lowers the NF. In such a way, the clamped gain of 16.3dB with a variation below 0.2dB and the noise figure below 5dB is achieved on the new L-band gain-clamped EDFA.

Broad-flattened bandwidth wavelength conversion based on difference-frequency generation in aperiodically poled lithium niobate

We propose a general routine, Genetic-Simulated Annealing method (GSA) for the optimal design of quasi-phase matched (QPM) non-uniform grating. Here this method is applied to the design of the flat broadened wavelength conversion bandwidth of 40-mm aperiodically poled lithium niobate (APLN) based on difference-frequency generation (DFG). The flat conversion bandwidth of APLN is broadened from the original 65nm in a 40-mm periodically poled lithium niobate (PPLN) to the pre-designated 130 nm in a 40-mm APLN, which conversion efficiency is 6.7 dB higher than that of 12.4-mm PPLN under the same conversion bandwidth.

Nonlinear effect process and its optimum of supercontinuum generation in dispersion-shifted fiber

We investigate theoretically the process of supercontinuum (SC) generation which results from four-wave mixing (FWM) taking into account the effects of self-phase modulation (5PM) and cross-phase modulation (XPM) in a dispersion-shift optical fiber. The optimum pump wavelength at the highestconversion efficiency of FWM is obtained under the condition of two pumps with a weak probe on a lossless dispersion-shifted fiber and three pumps with equal channel spacing on a fiber including fiber loss. We also investigate the effects of 5PM and XPM by the spectra of co-propagating pump pulses with different pump power and fiber length. Finally, we propose a way to obtain the optimal SC resulting in a highest efficiency of FWM with small effects of 5PM and XPM.