It is found that the supercontinuum spectrum is generated from cross-phase modulated soliton pulses which are propagated through a dispersion-flattened/decreasing fiber with low birefringence. The cross-phase modulation is achieved by exciting two orthogonally polarized modes in a birefringent fiber and the effect of input azimuth of linearly polarized pulses is discussed theoretically and numerically.

A temperature-tuned Fabry-Perot resonator fabricated by RF-sputtering Ag thin-film on both output end faces of a short piece of quasi-single mode fibers is presented. In order to analyze the modal properties of optical fibers composing a fiber-optic resonator, some unknown integers concerning with Fabry-Perot resonance modes are determined for a nominally circular-core fiber.

A cylindrical PZT around which some length of a fiber is wound is demonstrated as a component of optical phase shifter and modulator in a single-mode fiber interferometer. Its sensitivity under the operation of DC input mode is 0.18 π rad/V/meter in phase change at the optical wavelength of 6328 . Some characteristics of amplitude response linearity and frequency response uniformity for the AC drive voltage applied to the PZT cylinder are also discussed.

An interferometric method for measuring frequency deviation of semiconductor lasers in wide range of modulation frequencies has been developed. Fringe visibilities of an interfered IM- and FM-modulated light depend on frequency deviation, time delay difference and intensity modulation depth. The applicability of this method has been also discussed.

Average intensity of far-field radiation patterns of laser light emitting from an end face of the multimode optical fiber is theoretically analyzed by assuming a Gaussian autocorrelation function for the refractive-index inhomogeneities in an optical fiber. The average intensity distribution of far-field patterns is characterized by both the statistical scale of index fluctuations and the fiber parameters of core radius and refractive-index profile. It is shown that the on-axis maximum intensity decreases as the correlation length of refractive-index inhomogeneities becomes small compared with the wavelength of light, whereas the off-axis average intensity decays gradually with the increase of the distance from the axis. The average intensity distributions obtained here are found to be nearly Gaussian for both types of the optical fiber with step-index and graded-index profiles of the refractive index.

A new type of optical frequency domain reflectometry is demonstrated. Optical carrier frequency is swept so that a phase of the backscattered light is shifted. Then, an interference output of the backscattered light is Fourier transformed. The farther the scattering point locates, the faster the phase of the backscattered light changes. Hence, the Fourier spectrum of the interference output displays the fault distribution along a wave-guide. In the present scheme, the theoretical resolution is inversely proportional to the frequency sweeping range of the optical source and is given by z=c/2nf, where f is the frequency sweeping range of the optical source. In a preliminary experiment, a Michelson type interferometer in which a target fiber of 20cm length is inserted in a probing arm. The reference arm is adjusted to be longer than the probing arm by about 1.8m. This is because the interference term between the backscattering light and the reference light should be separated from the interference term formed by the backscattering light itself. A LD pumped Nd: YAG ring laser whose frequency sweeping range is 20GHz is used as a variable wavelength source. The calculated resolution is 5mm for n=1.5 in fiber. A resultant spectrum in which the two peaks correspond to the reflections at both the fiber ends is obtained.

It is reported firstly that spatial filtering of laser beam by a receiving optical system such as a finite-aperture detector causes harmonic distortions of a directly modulated semiconductor laser diode when the beam irradiance is reflected partially at the submount. The theory based on geometrical optics for interference of directly emerging light and reflected light is developed and the numerical results are presented for a variety of laser structures and FM-modulation parameters.

Modal noise in a quasi-single mode fiber propagating a few LP mode is studied experimentally by simulating lossy connectors and imperfectly coupled detectors. The signal-to-noise ratio of the so called two-mode fiber is found to be high as in the usual multimode fiber.