Wanjing Peng

A 1.97 μm multiwavelength thulium-doped silica fiber laser based on a nonlinear amplifier loop mirror

A 1.97 μm multiwavelength Tm-doped fiber laser based on a nonlinear amplifier loop mirror (NALM) has been experimentally demonstrated. The NALM with 500 m standard single mode fiber introduces intensity-dependent gain to alleviate mode competition caused by homogeneous gain broadening in Tm-doped fibers. At room temperature, up to 42 wavelengths with a wavelength spacing of 0.33 nm oscillate within a 10-dB bandwidth simultaneously. Repeat measurement of the laser spectrum shows the wavelength drift of a multiwavelength Tm-doped fiber laser is less than 0.05 nm in 40 min.

A stable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser with superimposed FBG and an in-line two-taper MZI filter

A simple approach to fabricate a stable single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser with one superimposed fiber Bragg grating (FBG) is proposed and demonstrated. The superimposed FBG is fabricated by the dual-exposure method for wavelength selection. A home-made in-line two-taper Mach?Zehnder interferometer is incorporated to balance the intra-cavity loss for the wavelengths. The SLM operation is guaranteed by a feedback fiber loop and saturable absorber. A stable dual-wavelength SLM fiber ring laser with a wavelength spacing of approximately 8.53?nm is experimentally realized. The optical signal-to-noise ratio of the laser output is over 50?dB and the linewidth of each wavelength measured by the delayed self-heterodyne method is 9.67?kHz and 9.07?kHz, respectively. The proposed scheme offers the possibility for difference frequency generation of terahertz radiation.

A multiwavelength thulium-doped silica fiber laser incorporating a highly nonlinear fiber

A multiwavelength Tm3+-doped silica fiber laser incorporating a highly nonlinear fiber is presented. In the laser cavity, a nonlinear polarization rotation (NPR) based fiber loop mirror is used to overcome the mode competition and a polarization-maintaining fiber Sagnac loop mirror is used as the filter. The 150 m highly nonlinear fiber can improve the NPR effect in the laser cavity, which can increase the number of output channels. By adjusting the polarization state of the polarization controllers properly, stable multiwavelength operation at the 2 μm spectrum can be obtained at room temperature. It can achieve 15 output channels within a 10 dB bandwidth from 1990 to 2007.5 nm. The channel spacing of the multiwavelength Tm3+-doped silica fiber laser is 1.22 nm. Moreover, the performance of the laser is investigated for different pump powers and fibers.

Temperature-Independent and Strain-Independent Twist Sensor Based on Structured PM-CFBG

In this letter, we present a structured polarization-maintaining chirped fiber Bragg grating (PM-CFBG) for temperature-independent and strain-independent twist measurement. The structured PM-CFBG, which has two transmission peaks, is created by tapering directly on the PM-CFBG. The grating transmissivity of structured PM-CFBG changes linearly with twist while it is insensitive to strain and temperature. The wavelength interval changes proportionally to the temperature, but remains the same as the strain increases. This novel sensor can be used to measure temperature, strain, and twist simultaneously.

Switchable and tunable dual-wavelength single-longitudinal-mode erbium-doped fiber laser with special subring-cavity and superimposed fiber Bragg gratings

A switchable and tunable dual-wavelength single-longitudinal-mode (SLM) erbium-doped fiber laser (EDFL) has been proposed and demonstrated. Two superimposed fiber Bragg gratings (SI-FBG) have been used as one original wavelength selection component. A special subring-cavity was employed to select the SLM. By properly adjusting a polarization controller, single- and dual-wavelength switchable operations with high wavelength and power stability were realized experimentally. Regardless of which work mode, the signal to noise ratio was higher than 60 dB and the polarization extinction ratio was higher than 20 dB. The wavelength-spacing was 9.96 nm, indicating that it can be used to generate continuous-wave terahertz waves. The linewidth of each lasing wavelength measured by the delayed self-heterodyne method was approximately 1.25 kHz and 1 kHz, respectively. By stretching the SI-FBG, the EDFL had a wavelength-tunable range of 5.96 nm in both the single- and dual-wavelength operations.

A high stability wavelength-tunable narrow-linewidth and single-polarization erbium-doped fiber laser using a compound-cavity structure

A high stability wavelength-tunable narrow-linewidth and single-polarization erbium-doped fiber laser using a compound-cavity structure is proposed and demonstrated experimentally. The compound-cavity is composed of a main-linear-cavity and a subring-cavity. Using a pump power of 150?mW, the optical signal to noise ratio of the laser output is as high as ?67?dB; the wavelength and output power fluctuation are 0.7?pm and 0.07?dBm respectively in an experimental period of 1?h; the linewidth of the laser output is as narrow as 650?Hz; the degree of polarization of the laser output is stable at a value of 100.8% in 15?min and the polarization extinction ratio is as high as 30.57?dB; the wavelength-tunable range is as wide as ?8.1?nm. The proposed fiber laser can be used in areas where high stability, narrow-linewidth, single-polarization and wide wavelength-tunable range are needed.

DFB laser based on single mode large effective area heavy concentration EDF

A π phase shifted distributed feedback (DFB) laser based on single mode large effective area heavy concentration erbium-doped fiber (EDF) has been demonstrated. The homemade EDF was fabricated by the modified chemical-vapor deposition (MCVD) technique, and the 13cm long π phase shifted fiber grating was written in the intracore of the EDF. The erbium-doped concentration is 4.19 × 10(25) ions/m(3), the mode field diameter of the fiber is 12.2801 um at 1550 nm, the absorption coefficients of the fiber are 34.534 dB/m at 980 nm and 84.253 dB/m at 1530 nm. The threshold of the DFB laser is 66 mW, and the measured maximum output power is 43.5 mW at 450 mW pump power that corresponding to the slope efficiency of 11.5%. The signal-to-noise ratio (SNR) of the operating laser at 200 mW input power is 55 dB, and the DFB laser has a Lorentz linewidth of 9.8 kHz at the same input pump power.

A switchable and wavelength-spacing tunable single-frequency and single-polarization dual-wavelength erbium-doped fiber laser based on a compound-cavity structure

A switchable and wavelength-spacing tunable single-frequency and single-polarization dual-wavelength erbium-doped fiber laser is proposed and demonstrated experimentally. The fiber laser is composed of a main linear cavity and two subring cavities. In dual-wavelength operation, the wavelength spacing can be tuned from 0.430?nm to 4.487?nm, showing that the fiber laser can be used for photonic generation of a microwave signal with a tunable frequency range from 54?GHz to 563?GHz; in single-wavelength operation, the fiber laser can either work at a fixed wavelength of 1544.108?nm or work at a wavelength with a tunable range of 4.057?nm, from 1544.538?nm to 1548.595?nm. The linewidths of two wavelengths are approximately 760?Hz and 810?Hz respectively. The polarization-extinction ratios of the laser outputs, both in dual- and single-wavelength operation, are higher than 30?dB.

A tunable self-seeded Brillouin/erbium fiber laser utilizing an asymmetrical twin core fiber based Mach?Zehnder interferometer

A tunable self-seeded Brillouin/erbium fiber laser (BEFL) utilizing an asymmetrical twin core fiber based Mach–Zehnder interferometer (ATCF-MZI) is proposed and demonstrated. The proposed self-seeded BEFL has the advantage of being able to generate up to 17 output channels with high optical signal to noise ratio (>10 dB). The Brillouin pump is self-seeded in the laser cavity instead of the extra Brillouin pumping. By bending the ATCF-MZI, an 8 nm wavelength-tunable range is achieved. This self-seeded BEFL shows linear tunability and good stability. Meanwhile, the experimental results indicate that the laser output with operation wavelength away from the free-running cavity mode has better output characteristics.

Stable High SNR Narrow Linewidth Linear Cavity Single-Wavelength Er-Doped Fiber Laser

A stable high signal to noise ratio (SNR) narrow linewidth linear cavity single-wavelength Er-doped fiber laser is reported. In the experiment, we used a fiber Bragg grating Fabry-Perot (FBG F-P) etalon and a Fiber Loop Mirror (FLM) as the reflectors of the laser cavity, and used a length of 4m Er-doped fiber as the saturable absorber to suppress mode hopping and stabilize frequency effectively. An all fiber polarization controller (PC) was used to restrain spatial hole burning effect in gain fiber. Using a length of 3m Er-doped fiber pumped by a laser diode at 975nm, stable single-wavelength laser at 1544.714nm was acquired, and the 3dB linewidth of laser was 0.013nm. The corresponding threshold of laser was 30mW, the SNR was as high as 70dB, and the slope efficiency was about 0.5%.