In this letter, a temperature sensor based on a fiber ring laser with a reflective Sagnac loop is proposed. The reflective Sagnac loop inserted into the fiber ring laser through a download optical fiber is used as the filter and sensing head to supply high temperature sensitivity. As the temperature varies, the transmission spectrum of Sagnac loop changes, leading to the shift of emission wavelength of a fiber ring laser. We obtain a temperature sensor system with a high temperature sensitivity of 1.739 nm/°C, a narrow 3-dB bandwidth less than 0.05 nm, and a high signal-to-noise ratio ~50 dB. Moreover, it is convenient to achieve the remote sensing by changing the length of the download optical fiber.

A single-frequency fiber laser operating at 1950 nm has been demonstrated in an all-fiber distributed Bragg reflection laser cavity by using a 1.9 cm commercially available thulium-doped silica fiber, for the first time, to the best of our knowledge. The laser was pumped by a 793 nm single-mode diode laser and had a threshold pump power of 75 mW. The maximum output power of the single longitudinal mode laser was 18 mW and the slope efficiency with respect to the launched pump power was 11%. Moreover, the linewidth and relative intensity noise at different pump power have been measured and analyzed.

We report the system design and experimental verification of an intracavity absorption multiplexed sensor network with hollow core photonic crystal fiber (HCPCF) sensors and dense wavelength division multiplexing (DWDM) filters. Compared with fiber Bragg grating (FBG), it is easier for the DWDM to accomplish a stable output. We realize the concentration detection of three gas cells filled with acetylene. The sensitivity is up to 100ppmV at 1536.71nm. Voltage gradient is firstly used to optimize the intracavity sensor network enhancing the detection efficiency up to 6.5 times. To the best of our knowledge, DWDM is firstly used as a wavelength division multiplexing device to realize intracavity absorption multiplexed sensor network. It make it possible to realize high capacity intracavity sensor network via multiplexed technique.

We demonstrate a high-resolution temperature sensor based on optical heterodyne spectroscopy technology by virtue of the narrow linewidth characteristic of a single-frequency fiber laser. When the single-frequency ring fiber laser has a Lorentzian-linewidth <1 kHz and the temperature sensor operates in the range of 3−85 °C, an average sensitivity of 14.74 pm/°C is obtained by an optical spectrum analyzer. Furthermore, a resolution as high as ~5 × 10⁻³ °C is demonstrated through optical heterodyne spectroscopy technology by an electrical spectrum analyzer in the range of 18.26–18.71 °C with the figure of merit up to 3.1 × 10⁵ in the experiment.

The output characteristics of a 2-μm all-silica-fiber single-frequency distributed Bragg reflector (DBR) laser in-band pumped by a 1570-nm fiber laser were investigated in this letter. More than 50-mW laser power was obtained in this all-silica-fiber laser system with the linewidth of ~ 36 kHz. Low relative intensity noise was achieved in the experiment due to the superior noise properties of 1570-nm fiber laser as pump source, especially at the relaxation oscillation frequency, where the noise intensity is measured to be as low as -112 dB/Hz. With another piece of Tm ³⁺ -doped fiber spliced directly to the DBR laser to effectively exploit the pump power, a compact hundred-mW single-frequency fiber laser at 1920 nm was obtained without performance degradation. The compact hundred-mW all-silica-fiber single-frequency laser system we demonstrated here can be a competitive candidate to promote the popularization of 2 μm single-frequency fiber laser for the applications such as free-space optical communication and LIDAR.