It is demonstrated that the constitution of complex Faraday rotation in presence of intrinsic birefringence. We analyze the relationships between incident azimuth of linearly polarized light and birefringence and the influence of different orders birefringence on the measurement of magneto-optical effect. We proposed a relatively simple technique to accurately measure Faraday rotation of fiber. The order of birefringence in optical fiber and the high sensitivity magnetooptical characteristics can be determined by the measurement system.
Magneto-optical fiber plays an important role in magneto-optical devices. The fiber has larger Verdet constant will lead to a larger Faraday rotation per unit length fiber and applied field. In order to increase the magneto-optical characteristic, especially the Verdet constant of photonic crystal fiber, a magneto-optical fiber device based on combination of the magnetic fluid and the tunable photonic bandgap effect of photonic crystal fiber is proposed. The magnetic fluid is filled into the air holes of the cladding layer in the photonic crystal fiber using a new air pressure-filled method. Because the magnetic fluid prepared in this experiment has higher refractive index (>1.45), and is filled into the air-holes of photonic crystal fiber, as a result, the index guiding fiber is converted into photonic bandgap fiber. A magneto-optic system based on the Stokes polarization parameters method is designed which could analyze the Faraday effect. The corresponding Faraday rotation could be measured in the external magnetic field with different magnetic intensity by this magneto-optic system. The Faraday rotation of the photonic crystal fiber filled with magnetic fluid is approximately 5 times than that of the single mode optical fiber. The proposed magneto-optical fiber device takes full advantage of the ultrahigh sensitivity characteristic of photonic bandgap fiber and the large Verdet constant of magneto-optical fiber, can be used for high sensitive magnetic field sensor, magneto-optical switch, and magneto-optical modulator, etc.
Remote optical fiber sensors for radiation measurement are very useful in high radiation fields. In this paper, we
fabricated scintillating optical fiber by using a cerium-doped silica rod. In the drawing process, we obtained different
fiber samples by changing the drawing temperature and speed. The drawing temperature is from 1900 to 2200 °C and the
speed is from 1 to 10 m/min. The experimental results showed that the optical rod physical properties such as viscosity,
tension and scintillating efficiency can be controlled by the parameters of temperature and speed. The optical properties
and chemical composition of the scintillating optical fiber have been analyzed by Raman spectra and X-ray fluorescence
spectrometer (XRF-1800, SHIMADZU). The concentration of the doped cerium is 0.55%. Moreover, a test system is
proposed to measure the scintillating performance of the fabricated optical fibers. For the scintillating properties, the
effect of fiber length, the number of fiber bundle and the detection angle were analyzed. Experimental results showed
that the optimal length of the cerium doped fiber is ~15 cm. The scintillating light intensity increases linearly with the
number of the fiber bundle. With two low intensity 60Co (0.2784 μCi) and 137Cs (1.0865 μCi) gamma radiation sources, the scintillating light can be detected the gamma sources by using the scintillating fiber sensor which is connected a MMF.
The Faraday magneto-optical effect of optical fiber has many applications in monitoring magnetic field and electric current. When a linearly polarized light propagates in the direction of a magnetic field, the plane of polarization will rotate linearly proportional to the strength of the applied magnetic field, which following the relationship of θF =VBl. θF is the Faraday rotation angle, which is proportional to the magnetic flux density B and the Verdet constant V .
However, when the optical fiber contains the effect of linear birefringence, the detection of Faraday rotation angle will depend on the line birefringence. In order to determine the Verdet constant of an optical fiber under a linear birefringence, the fiber birefringence needs to be accurately measured. In this work, a model is applied to analyze the polarization properties of an optical fiber by using the Jones matrix method. A measurement system based on the lock-in amplifier technology is designed to test the Verdet constant and the birefringence of optical fiber. The magnetic field is produced by a solenoid with a DC current. A tunable laser is intensity modulated with a motorized rotating chopper. The actuator supplies a signal as the phase-locked synchronization reference to the signal of the lock-in amplifier. The measurement accuracy is analyzed and the sensitivity of the system is optimized. In this measurement system, the Verdet constant of the SMF-28 fiber was measured to be 0.56±0.02 rad/T·m at 1550nm. This setup is well suitable for measuring the high signal-to-noise ratio (SNR) sensitivity for lock-in amplifier at a low magnetic field strength.