| 摘要 |
<p>PURPOSE:To make smaller a tracking error in comparison with that of a device where indirect monitor is conducted in the successive stage of a laser diode by obliquely cutting the end part of an optical fiber which receives the front end emitting light of laser diode and then inputting reflected laser beam at the cutting surface into a photosensitive element for monitoring. CONSTITUTION:The end part of an optical fiber 11 is obliquely cut and a light input surface of a photodiode 14 used for monitoring is directioned to the laser reflecting direction from the cutting surface in the end part of optical fiber 11 and position of such light input surface is adjusted so that the optimum light input can be obtained. A cutting angle theta of the end part of optical fiber 11 is limited within 45 deg. in order to provide sufficient amount of incident light to the optical fiber 11 and the optimum angle theta is determined considering an output level of laser module and photodiode 14 within the range that the reflected laser beam does not return to the laser diode 13. With this method, variation of optical output from the optical fiber due to difference of temperature characteristic of laser diode on the front and rear side of laser can be prevented.</p> |
