Microstructure and properties of novel polarization maintaining fiber

An improved type of elliptical jacket polarization maintaining fiber was developed by using a modified chemical vapor deposition method with special treatment. Different from conventional elliptical jacket, the shape of the stress jacket was transmuted. The cross-section of fiber consists of 5 layers: substrate, outer cladding, stress jacket, inner cladding and core. The cross sectional component distribution was investigated by electron probe microscopy and energy dispersive spectrum. The finite element method was used to calculate the stress birefringence. Based on the analyses of the microstructure, the technological process is improved. The temperature cycling test of the fiber wound into gyroscope coils was performed. The results show that the fiber possesses superior performance at high and low temperatures compared with other fibers. The high homogeneity is achieved by well-controlled modified chemical vapor deposition process. A homogeneous length of 8 km fiber is obtained. With advantages in homogeneity and length, the fiber has great potential in applications such as fiber gyroscopes, fiber hydrophone and other optical fiber sensors.

Refractive index and temperature sensing characteristics of an optical fiber sensor based on a tapered single mode fiber/polarization maintaining fiber

An evanescent field optical fiber sensor based on a short section of polarization maintaining fiber spliced with a tapered single mode fiber is proposed and experimentally investigated. We mainly focus on the refractive index （RI） and temperature sensing characteristics of this compact device. The transmission spectrum of the resonance wavelength, induced by the interference between the excited low order cladding modes and core modes, shows the quadratic function relationships with RI and linear relationships with temperature. Thus, the proposal of this simple-to-fabricate, compact, and low cost sensor shows its possible potential in the sensitive detection field.

Low-repetition-rate, all-polarization-maintaining Yb-doped fiber laser mode-locked by a semiconductor saturable absorber

A low-repetition-rate, all-polarization-maintaining（PM）-fiber sub-nanosecond oscillator is presented, which is simple and low-cost, composed of standard components. The ring cavity is elongated by 114-m-long standard PM fiber, and passively mode-locked by a fiber pigtailed semiconductor saturable absorber. Linearly polarized pulses with 1.66 MHz repetition rate and 22 dB polarization extinction ratio are generated at a wavelength of 1030 nm, which is determined by an intracavity filter. In addition, to demonstrate that the oscillator is a good seed for high energy pulse generation, an all-fiber master oscillator power amplifier is built and amplified pulses with energy about 2 μJ are obtained.

Low Loss Polarization Maintaining Photonic Crystal Fiber

A low loss polarization maintaining photonic crystal fiber has been fabricated. The fiber loss was 1.3 dB/km at 1550 nm. The polarization crosstalk for a 100-m fiber was -35 dB at 1550 nm.

Fiber transmission demonstrations in vector mode space division multiplexing

Much attention has been focused on the use of scalar modes for space division multiplexing （SDM）. Alternative vector mode bases offer another solution set for SDM, expanding the available trade-offs in system performance and complexity. We present two types of ring core fiber conceived and designed to explore SDM with fibers exhibiting low interactions between supported modes. We review demonstrations of fiber data transmis- sion tbr two separate vector mode bases： one for orbital angular momentum （OAM） modes and one for linearly polarized vector （LPV） modes. The OAM mode demon- strations include short transmissions using commercially available transceivers, as well as kilometer length transmission at extended data rates. The LPV demonstra- tions span kilometer length transmissions at high data rate with coherent detection, as well as a radio over fiber experiment with direct detection of narrowband signals.

A switchable and tunable ytterbium-doped fiber ring laser with a Sagnac loop mirror

A switchable and tunable ytterbium-doped fiber ring laser(YDFL) is reported and demonstrated. Employing a Sagnac loop mirror fabricated by an 85-cm-long polarization-maintaining fiber(PMF), the proposed YDFL can operate with stable dual-wavelength lasing or tunable single-wavelength lasing around 1 064 nm. Both stable dual-wavelength lasing and tunable single-wavelength lasing are achieved by adjusting a polarization controller in the Sagnac loop mirror. The experimental results show that the output of the proposed fiber laser with two different operation modes is rather stable at room temperature.

Periodical rocking long period gratings in PANDA fibers for high temperature and refractive index sensing

We report periodical rocking long period gratings(PR-LPGs) in PANDA fibers fabricated with CO_2 laser. The PR-LPGs achieve very high coupling efficiency of 19 dB with 12 periods and a 3.5° twist angle in just one scanning cycle, which is much more effective than the conventional CO_2 laser fabrication technique. This type of LPGs exhibits polarization-selective resonance dips which demonstrate different sensitivities to environmental parameters. The high temperature and external refractive index sensitivities are measured simultaneously, so it can be used as a wavelength-selective polarization filter and sensor.

Intermodal interference of LP_(01) and LP_(11) modes inpanda fibers

LP01 and LP11 mode interferences in high-birefringence（Hi-Bi） panda fibers are theoretically and exper-imentally presented.The propagation characteristics of both the fundamental and second-order modes in Hi-Bi panda fibers are investigated,and the interference output intensity distribution of the LP01 and LP11 modes in panda fibers are thoroughly examined.An experiment is conducted to verify the feasibility of modal interference sensors.The results show that the two-lobe interference pattern of panda fibers generates energy exchanges when external strain is applied on the fiber.Moreover,Hi-Bi panda fibers can be used to design voltage sensors.

Hybrid fiber interferometer for simultaneous measurement of displacement and temperature

A hybrid fiber interferometer sensing configuration for displacement and temperature measurements is proposed and experimentally demonstrated that is constructed by splicing a short section of polarization maintaining op- tical fiber to an end-cleaved single mode optical fiber with a tapering structure. The reflected spectrum changes with the variation of displacement and temperature. The sensing configuration uses the method of wavelength and intensity modulations for displacement and temperature measurements, respectively, to which the sensitiv- ities are 0.01392 nm/μm, 0.0214 dBm/μm, --0.09136 nm/℃, and 0.15795 dBm/℃. Experimental results show that displacement and temperature can be measured simultaneously by demodulating the reflected spectrum.

High Sensitivity Temperature Sensor Based on Harmonic Vernier Effect

A high-sensitivity temperature sensor based on the harmonic Vernier effect is proposed and verified by experiments.The main component of the sensor is a Sagnac interferometer consisting of two sections of polarization maintaining fibers(PMFs)spliced with an intersection angle of 45o between their fast axes.The harmonic Vernier effect is achieved by setting the length of one of the PMFs an integral multiple(i-times)of the length of the other plus a detuning factor.Compared with the Sagnac interferometer based on the fundamental Vernier effect,the temperature sensitivity of the harmonic Vernier effect is higher,reaching i+1 times of that of the fundamental Vernier effect(i is the order of the harmonic).