Abstract: The present invention relates to a wavelength-swept laser and a method for generating laser output. The wavelength-swept pulse laser according to one aspect of the present invention uses spontaneous mode-locking to produce a pulse output with the center wavelength continuously varying with time. On the contrary, the wavelength-swept laser according to another aspect of the present invention suppresses mode-locking to produce continuous output by tuning the filter frequency change speed to the frequency shift speed of the frequency shifter. The lasers of the present invention are applicable to optical sensing or WDM optical communication.

Abstract: Disclosed is an apparatus and method for measuring a changing amount of insertion loss of an optical device depending on a polarization state of an incident light, i.e., a polarization-dependent loss. An incident light that is periodically subject to all polarization states passes through a testing optical device by a polarization scrambler including a piezoelectric element type optical fiber birefringence modulator, and an optical detector measures intensity of the passing light, in which the measured intensity values are averaged for birefringence modulation having a constant period, and then the polarization-dependent loss is computed from a ratio of maximum power to minimum power for the period. Use of the birefringence modulator shortens measuring time, and decreases an affect of external disturbance to the incident light that is incident into the testing optical component or occurrence probability of the external disturbance, so that the polarization-dependent loss can be precisely measured.

Abstract: An apparatus and method for detecting the state of polarization (SOP). The apparatus of the present invention includes a phase retarder and a polarizer which rotate with different speeds. In the method of the present invention, optical signals passed through the rotating phase retarder and the rotating polarizer are detected and their harmonic components related to rotating frequencies of phase retarder and polarizer are analyzed, which gives the Stokes parameters representing the state of polarization. According to the present invention, the amount of phase retardation at the phase retarder can be obtained together with the state of polarization using frequency component analysis, reducing measurement errors. The present invention has advantages in SOP measurement of wide wavelength range, increasing the measurement accuracy.

Abstract: This invention relates to optical devices such as a fiber-optic frequency shifter and an optical interferometer. This invention also relates to a method of generating optical interference signals to obtain reliable sensor signals independent of polarization fluctuations of the optical waves in the fiber. Fiber-optic interferometers have many advantages such as high sensitivity and convenient way of using even in poor surrounding environments. These interferometer, however, exhibit polarization dependent signal degradation since the polarization of a light wave passing through an optical fiber irregularly changes depending on the birefringence of the fiber. This invention is characterized in that the frequencies of two orthogonal eigen polarizations of a light wave are shifted to different frequency values at one optical path of the interferometer. They produce two beat interference signals after interfering with the light wave passed through the other optical paht of the interferometer.

Abstract: The present invention relates to a fiber grating which introduces a plurality of asymmetric microbends in a fiber. The present invention also relates to fiber optic devices, such as a fiber-optic filter, a fiber-optic polarizer, a fiber-optic wavelength tunable bandpass filter, a fiber-optic frequency shifter, using the above fiber grating which has asymmetric mode-coupling characteristics. The optical devices of the present invention exhibit a high mechanical durability and a long-term stability of the device, degradation of the optical fiber device due to a change in the characteristics of the grating can be prevented even after a long time at high temperature. In particular, the fiber grating according to the present invention has asymmetric mode coupling characteristics, so that it can be prevalently applied to an optical fiber notch filter, an optical fiber polarizer, an optical fiber wavelength tunable bandpass filter, an optical fiber frequency shifter and so on.

Abstract: An optical fiber polarization scrambler decreasing the degree of polarization (DOP) of light efficiently using at least two optical fiber birefringence modulators (10, 11) and an operating parameter input method for the same. Birefringence modulators are constructed with hollow cylindrical piezo devices (10, 11) and a strand of optical fiber (30) wound continuously on the outer walls of the piezo devices (10, 11). An angle between the birefringence modulators consisting of the optical fiber polarization scrambler is configured to compensate the effect of circular birefringence. A method for exactly configuring birefringence modulation frequency and birefringence modulation amplitude to achieve effective polarization scrambling for the optical fiber polarization scrambler is also provided.

Abstract: An optical fiber polarization controller which has compact size by employing wave plates made of short sections of a first optical fiber having inherent birefringence such as a polarization maintaining optical fiber. In the control of the polarization state of input light, a second optical fiber, for example a single mode fiber, connected to the first optical fiber is twisted using fixing knobs, thereby rotating the birefringence axis of the first optical fiber with respect to the second optical fiber.