A kind of fiber-optic modulation-depth-tunable modulator is developed in this paper. In this modulator, a magnetic fluid is used as the cladding of the drawn fiber, which attenuates the evanescent field when the light is guided in the fiber. Because the attenuation depends on the strength of the applied external magnetic field, the emergent light intensity from the fiber is modulated with the change of the magnetic field strength. The response times, i.e., the span for the light intensity to reach the final steady value from the time when the magnetic field is turned on or off, are evaluated quantitatively.

A simple method based on the retroreflection on the fiber-optic end face is developed to measure the refractive index of a magnetic fluid in this letter. The measuring principle, accuracy, and sensitivity of this method are analyzed theoretically, and high precision and resolution can be achieved in principle. Experimental measurements are done to investigate the concentration and temperature dependent refractive index of the magnetic fluid. The linear dependence relation is obtained for both cases. The thermo-optical coefficient of the magnetic fluid is measured to be around −2.4×10−4°C−1.

In nonlinear optical frequency conversion process, it is desirable to maximize the product of the intensity of pump laser and the interaction length in order to achieve maximum conversion efficiency. In this paper, long and unbroken submicron-diameter optical fibers with low optical loss about 0.1dB/cm were fabricated with a new drawing process by heating the conventional single mode fiber using a designed electric strip heater. Pumped by a 532 nm mode-locked pico-second laser, enhanced SRS phenomena can be observed in the submicron-diameter fibers with relative low pump power.

A kind of tunable magnetic fluid grating is developed in this letter. The operating principle of the tunable magnetic fluid grating is analyzed theoretically. When the absorption coefficient modulation of the grating is not too large, the energy of the zeroth-order diffracted light can be transferred to that of the higher-order completely and vice versa. Experiments are done to investigate the tunable diffraction properties of the magnetic fluid grating, and the transfer of the energy of the zeroth-order diffracted light to that of the higher-order is apparent.

This letter presents a tunable optical fiber filter based on a long-period grating (LPG) by applying a magnetic field on a magnetic nanoparticle fluid. The movement of the magnetic fluid jacket surrounding the fiber cladding controlled by an applied magnetic field results in a variation of the external index between that of the magnetic fluid and air. As a result, the attenuation band of the LPG is shifted. The observed center wavelength shift of the attenuation band is as large as 7 nm, which can cover eight dense wavelength division multiplexing channels (100 GHz channel spacing). Repeatable transport of a magnetic fluid at a switching rate of 1 Hz is demonstrated.