Anritsu Corporation

Hiroaki Endoh

Muneo Ishiwata

Yasuaki Nagashima

Hiroshi Goto

Hiroaki Ohtateme

Akihiko Asai

Ko Ikeuchi

To obtain a predetermined power intensity without influencing the wavelength of output light by external APC, a laser beam having a predetermined plane of polarization and output from a tunable wavelength light source passes through a Faraday element and a polarizer constituting an optical attenuator and is split into a split light beam and an output light beam by a beam splitter. The split light beam is received by a light-receiving device, and a detection signal according to the power intensity is output from the light-receiving device. A controller supplies a signal according to the difference between the detection signal output from the light-receiving device and a set value set at an intensity setting device to a coil of the Faraday element constituting the optical attenuator. The plane of polarization of the laser beam output from the Faraday element is rotated with respect to the plane of polarization of the polarizer, thereby controlling the attenuation amount of the optical attenuator such that the detection signal output from the light-receiving device always equals the set value.

Tunable wavelength light source apparatus for stabilizing power

A sawtooth generates a sawtooth wave having a high response speed and good linearity with a simple arrangement in converting a change in phase of an input signal into a linear level change. A signal interpolating apparatus uses this sawtooth wave to output a predetermined signal (interpolation signal) every predetermined phase change of the input signal with a simple arrangement. An arithmetic operation section receives two sinusoidal signals A and B having equal periods and phases which are offset by 90.degree. and with respect to each other, obtain a signal X=A/(B+a) and a signal Y=A/(B+B) using constants .alpha. and .beta. respectively satisfying B+.alpha..apprxeq.0 and B+.beta..apprxeq.0. A switching unit selects the linear ramp portions of the signals X and Y to output a continuous sawtooth wave. On the basis of the value of this sawtooth wave, a desired interpolation signal is output from a memory which stores predetermined data.

Sawtooth generator and signal interpolating apparatus using the same

In an external-cavity tunable wavelength light source using a semiconductor laser (LD), an oscillation wavelength is tuned by simultaneously changing a current to be injected to the phase adjustment area of the LD and the rotation angle of a diffraction grating while holding the same external cavity longitudinal mode. A light beam emitted from the AR-coated end face of the LD having the phase adjustment area is collimated by a lens and incident on the diffraction grating. Only a light component having a specific wavelength selected upon spectral dispersion is reflected by the diffraction grating and returns to the LD. With this operation, an external cavity (effective cavity length K) is formed between the LD and the diffraction grating, thereby performing laser oscillation at a wavelength determined by an external cavity longitudinal mode and the cavity loss of the diffraction grating. The effective cavity length K can be changed in accordance with the current to be injected to the phase adjustment area. A current injection unit injects the current to the phase adjustment area. An oscillation wavelength control unit controls the injection current output from the current injection unit and the rotation angle of the diffraction grating.

Growing community of inventors

Isehara, Japan

Hiroaki Endoh