Optical pulse tester using light emitting device

Abstract

To provide a small and high-performance optical pulse tester using a light emitting device including semiconductor light emitting element capable of emitting light beams with wavelengths in a plurality of wavelength ranges with a high optical output. An optical pulse tester includes: a light emitting device including a semiconductor light emitting element having first and second light emitting end facets formed by cleavage respectively, and a light emitting element driving circuit which applies a driving current to each of a plurality of active layers; a light receiving section which converts returned light of the optical pulse from the optical fiber to be measured into an electric signal; and a signal processor which analyzes a loss distribution characteristic of the optical fiber to be measured on the basis of the electric signal converted by the light receiving section.

1 . An optical pulse tester comprising:
 a light emitting device including: a semiconductor light emitting element having first and second light emitting end facets formed by cleavage respectively, in which a plurality of active layers having gain wavelengths in different wavelength ranges are disposed on a semiconductor substrate so as to be optically coupled in a guiding direction of light from the first light emitting end facet toward the second light emitting end facet in order of the length of the gain wavelength, a lower electrode is formed on a bottom surface of the semiconductor substrate and a plurality of upper electrodes for applying a driving current to each of the plurality of active layers is formed above the plurality of active layers, at least one diffraction grating with a Bragg wavelength equivalent to a short gain wavelength is formed near an active layer with the short gain wavelength between two adjacent active layers and near the interface between the two active layers, and light generated in an active layer with a longest gain wavelength oscillates in a resonator formed by the first and second light emitting end facets and light generated in an active layer with a short gain wavelength oscillates in a resonator formed by the diffraction grating and the second light emitting end facet and both the light beams are emitted from the second light emitting end facet; and a light emitting element driving circuit which applies a driving current to each of the plurality of active layers and which short-circuits the upper electrode provided above an active layer with a short gain wavelength to the lower electrode provided on the bottom surface of the semiconductor substrate so that when a driving current is applied to one of the plurality of active layers, a leakage current does not flow into an active layer with a shorter gain wavelength adjacent to the active layer to which the driving current is applied, in which the driving current applied by the light emitting element driving circuit has a pulse form so that the semiconductor light emitting element emits an optical pulse and the light emitting device outputs the optical pulse emitted from the second light emitting end facet of the semiconductor light emitting element to an optical fiber to be measured;   a light receiving section which converts returned light of the optical pulse from the optical fiber to be measured into an electric signal; and   a signal processor which analyzes a loss distribution characteristic of the optical fiber to be measured on the basis of the electric signal converted by the light receiving section.   
     
     
         2 . The optical pulse tester according to  claim 1 ,
 wherein a reflectance with respect to light emitted from the second light emitting end facet of the semiconductor light emitting element is set to be lower than a reflectance with respect to light emitted from the first light emitting end facet of the semiconductor light emitting element.   
     
     
         3 . The optical pulse tester according to  claim 1 ,
 wherein the plurality of active layers of the semiconductor light emitting element includes first and second active layers,   the gain wavelength of the first active layer is 1.52 to 1.58 μm, and   the gain wavelength of the second active layer is 1.28 to 1.34 p.m.   
     
     
         4 . The optical pulse tester according to  claim 2 ,
 wherein the plurality of active layers of the semiconductor light emitting element includes first and second active layers,   the gain wavelength of the first active layer is 1.52 to 1.58 μm, and   the gain wavelength of the second active layer is 1.28 to 1.34 μm.   
     
     
         5 . The optical pulse tester according to  claim 1 ,
 wherein the plurality of active layers of the semiconductor light emitting element includes first to third active layers,   the gain wavelength of the first active layer is 1.60 to 1.65 μm,   the gain wavelength of the second active layer is 1.52 to 1.58 μm, and   the gain wavelength of the third active layer is 1.28 to 1.34 μm.   
     
     
         6 . The optical pulse tester according to  claim 2 ,
 wherein the plurality of active layers of the semiconductor light emitting element includes first to third active layers,   the gain wavelength of the first active layer is 1.60 to 1.65 μm,   the gain wavelength of the second active layer is 1.52 to 1.58 μm, and   the gain wavelength of the third active layer is 1.28 to 1.34 μm.