High Birefringence Fiber Sagnac Research Articles

Magnetic field fiber sensor based on the magneto-birefringence effect of magnetic fluid

In this study, the magneto-birefringence effect of magnetic fluid (MF) is adopted to form an innovative fiber optic magnetic field sensor. The sensitive section is fabricated via a D-shaped microstructure inscribed in a high-birefringence fiber Sagnac loop with a femtosecond laser. The D-shaped microstructure facilitates good combination of the optical-fiber Sagnac interferometer with the magneto-birefringence effect of MF without suffering from absorption loss and manual alignment. Experimental results show the good performance of the magnetic field fiver sensor, particularly its high stable extinction ratio. Preliminary results are provided, and the magnetic field sensitivity of 0.0823nm/mT can be further improved by increasing the depth and length of the D-shaped microstructure.

Strain and Temperature Discrimination Using High Birefringence Fiber Sagnac Interferometer With Enhanced Sensitivities

Discrimination between the strain and temperature variations based on the Sagnac interferometer is newly proposed and demonstrated with much improved properties. It is achieved by containing five sections of high birefringence fibers (HBFs) in the Sagnac interferometer-three of them spliced together act as the compact sensing head and the other two are isolated from the strain and temperature changes. By properly setting all the HBF lengths and relative orientations of their primary polarization axes, the strain and temperature sensitivity coefficients of the two wavelength dips generated due to the Sagnac interference may be greatly enhanced with the effectively reduced cross sensitivity.

Theory and experiment of flat-top all-fiber comb filter based on two high birefringence fiber Sagnac loop filters

A simple flat-top all-fiber comb filter based on two high birefringence fiber (HBF) Sagnac loop filters is presented. The proposed flat-top comb filter consists of two HBF Sagnac loop filters with two polarization controllers (PCs) and a fiber circulator. According to the theoretical analysis, with proper settings of the polarization state of the PCs, the comb filter can realize flat-top passband and the channel spacing also can be switched when the comb filter is convex spectrum. The 0.3dB bandwidth of the flat-top passband is 0.49nm with a free spectral range of 1.4nm. The maximum extinction ratio is nearly 20dB. The comb filter with switchable channel spacing can be obtained from 0.7nm to 1.4nm.

An FBG Strain Sensor Demodulation Technique Using Temperature- Compensation HBF Sagnac LM

A novel method of a fiber Bragg grating (FBG) stain sensor demodulation technique is presented. An experimental system is built up in which high birefringence fiber (HBF) Sagnac loop mirror (LM) is used as the edge filter. In order to improve the temperature stability of the system, we have experimentally demonstrated that packaged HBF can compensate the temperature shit of the HBF Sagnac LM filter. The shift of wavelength for an uncompensated HBF Sagnac LM is approximately 2.3nm/0C, and that of the compensated HBF Sagnac LM is 0.03nm/0C, which is much less than that of the uncompensated HBF Sagnac LM filters. Using the temperature-compensation HBF Sagnac LM, We achieve linear demodulation of FBG strain sensor with a range of about 1900 and the strain sensitivity is about 0.14 w/ .

Comb Spectrum Shaping Effect of a Fiber Sagnac Loop on an All-Normal-Dispersion Yb-Doped Mode-Locked Fiber Laser

In this letter, a high birefringence fiber (HBF) Sagnac loop is adopted in an all-normal-dispersion (ANDi) Ytterbium-doped (Yb-doped) passively mode-locked fiber laser. The HBF Sagnac loop acting as a comb spectrum filter has properties of controllable wavelength spacing and tunable transmission wavelength in the laser. With these properties of the HBF Sagnac loop filter, the laser offers a wide range of lasing performance. In the experiment, by changing the HBF length and adjusting the polarization within the loop, obviously different spectral profiles are observed, and broad wavelength tunability is also achieved. <?Pub _bookmark="" Command="[Quick Mark]"?>

Measuring chromatic dispersion of optical fiber using time-of-flight and a tunable multi-wavelength semiconductor fiber laser

We have developed a tunable multi-wavelength semiconductor fiber laser (SFL) for chromatic dispersion measurements of optical fiber based on the time-of flight (TOF) or pulse-delay technique. The SFL incorporates a programmable high-birefringence fiber Sagnac loop to select the separation of the lasing wavelengths between 3.2 and 1.6 nm. The SFL emits 5 and 11 wavelengths for separations of 3.2 and 1.6 nm, respectively, all within the C-band and with an output power uniformity within 3.2 dB. Results from TOF measurements are compared with standard phase-shift techniques; the percent differences between the two methods are within ±1.34% for measurements on various lengths of standard single mode fiber.

Tunable multi-wavelength all-fiber Raman source using fiber Sagnac loop filter

A multi-wavelength source is demonstrated in a cascaded-Raman fiber ring laser configuration using a tunable dual-section high birefringence fiber Sagnac loop filter. Depending on the pump powers and the cavity configurations, the source operates in the different wavelength regime between the 1120 and 1580 nm via cascaded Raman Stokes generation. The source generate up to 20 wavelength channels within the different orders of Raman Stokes wave regime with 0.4 nm channel spacing. The channel separation and the absolute wavelength of the multi-wavelength output are tunable and we show a discrete wavelength spacing of multi-wavelength output from 0.4 to 3 nm and continuous wavelength tuning over the wavelength channel spacing.