JPH05257081A - Optical transmitter - Google Patents

Abstract

PURPOSE:To provide the optical transmitter which multiplexes plural light signals by using one prism so that they are directed as specified. CONSTITUTION:The projection light beams of light emitting elements 1a and 1b are converted by lenses 2a and 2b into parallel light beams, which are made incident on incidence surfaces 4a and 4b of the prism 3 at right angles respectively. The incident light beams travel in the prism 3 and exit from projection surfaces 5a and 5b. The vertical angle alpha that the two projection surfaces 5a and 5b contain is determined corresponding to the refractive index (n) of the prism 3 so that the projected pieces 6a and 6b of luminous flux become parallel to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmitter suitable for a device for spatial light transmission, and more particularly to an optical transmitter for emitting signal light from a plurality of light emitting elements in a specific direction.

[0002]

2. Description of the Related Art Conventionally, the output power of a transmitter for spatial light transmission is generally limited by the maximum rated output of a light emitting element itself such as a semiconductor laser or a light emitting diode. When this optical transmitter is required to have an optical output exceeding the maximum rating of the light emitting element, an optical element having wavelength selectivity for optical signals from a plurality of light emitting elements having different wavelengths, such as a diffraction grating and a dielectric multilayer. A method of wavelength-multiplexing using an interference film or the like, and a method of polarization-multiplexing an optical signal from an element having a polarization characteristic such as a semiconductor laser with a polarizing element are known as output power combining methods.

[0003]

The conventional optical power combining method described above has the following drawbacks.

The first wavelength multiplexing method has a problem that it is difficult to freely select the emission wavelength of the light emitting element. In particular, in order to maintain the predetermined emission wavelength, the emission wavelength of the light emitting element generally depends on the temperature, so that accurate temperature control is required. Furthermore, since an optical element having wavelength selectivity is used, the structure of the optical transmitter becomes extremely complicated, and the size of the device becomes large and the cost becomes high.

In the second polarization multiplexing method, P-polarized light and S-polarized light are used.
If only the polarization can be multiplexed and the required output power cannot be obtained by this, it is necessary to combine it with the above wavelength multiplexing method, and there is a drawback that the feasibility is poor.

[0006]

SUMMARY OF THE INVENTION An optical transmitter according to the present invention includes N (N is a plurality) light emitting elements each emitting a light beam, and N converting each light beam from each light emitting element into parallel light. Parallel light from each of the lenses and each of the parallel light from each of the lenses is incident from each of the N input surfaces symmetrically formed about the central axis, and each of the parallel light incident from each of the N output surfaces is parallel to each other. And a prism for outputting to.

[0007]

The present invention will be described below with reference to the drawings. FIG. 1 is a principle diagram of an embodiment of the present invention.

The optical transmitter of FIG. 1 shows a case where the multiplicity N of the optical signal is 2 for the sake of simplicity. Light emitted from the light emitting elements 1a and 1b is respectively reflected by the lens 2a.
And 2b are converted into parallel light, and these parallel lights are vertically incident from the incident surfaces 4a and 4b of the prism 3, respectively. Incident light (parallel light) incident on the prism 3 travels through the prism 3 and exits 5a and 5b.
From each of which the light beams 6a and 6b are emitted. Here, the apex angle α formed by the two emission surfaces 5a and 5b of the prism 3 is determined according to the refractive index n of the prism 3 so that the light beams 6a and 6b are parallel to each other. Therefore, the light beams 6a and 6b are emitted from the prism 3 in parallel with each other.

When the multiplicity is N larger than 2, it is sufficient to form N incident surfaces 4a to 4n and emission surfaces 5a to 5n around the central axis of the prism 3 under the above conditions. By increasing the multiplicity N in this way, a larger optical transmitter output power can be obtained. Further, it goes without saying that the light emitted from the light emitting elements 1a and 1b can be modulated by a communication signal.

[0010]

As described above, according to the present invention, a single prism is used to multiplex a plurality of optical signals so that they are directed in a fixed direction. Therefore, the structure is extremely simple, and the size and cost are high. There is an effect that an output optical transmitter can be easily realized.

[Brief description of drawings]

FIG. 1 is a principle diagram of an embodiment of the present invention.

[Explanation of symbols]

 1a, 1b Light emitting element 2a, 2b Lens 3 Prism 4a, 4b Incident surface 5a, 5b Emission surface 6a, 6b Luminous flux

Claims (1)

[Claims] 1. N (N is a plurality) light emitting elements that emit light fluxes respectively, N lenses that convert the light fluxes from each of the light emission elements into parallel light, and parallel light from each of the lenses. And prisms for respectively injecting light from the N input surfaces, which are formed symmetrically with respect to the central axis, and outputting the incident parallel lights from the N output surfaces in parallel with each other. Optical transmitter.