We constructed a standard measurement setup for polarization mode dispersion (PMD) based on Jones matrix eigen-analysis method. We measured a differential group delay of a 1 m-long polarization maintaining fiber (PMF) and evaluated the measurement uncertainty to be less than 0.6 %. As a transfer standard for PMD, we fabricated mode-coupled PMD artifacts by concatenating the 50 PMF sections with random birefringent axis orientation. Using the standard setup, we certificated the PMD values of the three PMD artifacts to be 0.0884 ps, 0.977 ps, 1.541 ps with the standard uncertainty of 0.4 fs, 16 fs, 23 fs, respectively.
Continuous monitoring of soil movements is important to maintain civil structures. Fiber optic sensors can give the sensing solution for continuous displacement monitoring because they can be multiplexed with various sensors on one line of optical fiber, have the durability to harsh environments, and also are not affected by electro-magnetic effects. In this study, we work on the development of a multiplexed optical loss based fiber optic sensor for measuring displacements using the signal difference between the two reflected signals from a pair of optical connectors with various bending losses between them through an optical time domain reflectometer. We fabricate a multiplexed optical loss based fiber-optic sensor detecting linear displacements of 5 measuring positions of an object by setting these new 5 fiber-optic sensor probes on a single mode fiber simultaneously. We find that these sensors have a good capability to measure the displacements.
We describe the experimental construction of a single longitudinal mode Er-doped fibre ring laser incorporating a ring resonator filter. The system is designed to avoid mode hopping and may be frequency scanned for spectroscopic sensor applications.
We describe the results of experimental investigations of a bidirectional Er-doped fiber ring laser for its output power and the rotation rate dependent beat signal. Enhanced gyroscope beat signal is demonstrated by using an AM mode- locked Er-doped fiber ring laser.
Intrinsic Fabry-Perot optical fiber sensors were embedded to the tensile side of the 20 cm by 20 cm by 150 cm cement concrete structures. The sensors were attached to the reinforcing steels and then, the cement concretes were applied. It took 30 days for curing the specimens. After that, the specimens were tested with 4-point bending method by a universal testing machine. Strains were measured and recorded by the strain gauges embedded near optical fiber sensors. Output data of fiber sensor showed good linearity to the strain data from the strain gauges up to 2000 microstrain. The optical fiber sensors showed good response after yielding of the structure while embedded metal film strain gauges did not show any response. We also investigated the behavior of the optical fiber sensor when the specimens were broken down. In conclusion, the optical fiber sensors can be used as elements of health monitoring systems for cement concrete infra-structures.
Fiber laser sensors based on rare-earth doped fiber lasers have potential advantages over conventional fiber optic interferometric sensors with their simplicity in both the optical configuration and the electronic signal processing.[1,2] A ring laser gyroscope(RLG) built with rare-earth doped fiber amplifier has not been seriously investigated due to a few potential problems including gain competition between the two laser signals oscillating in opposite directions.
The polarization and modal properties of fiber lasers are theoretically and experimentally analyzed. The polarization properties of the fiber laser is advantageously applied to a novel form of fiber laser sensor.