Optical waveguides – With disengagable mechanical connector – Optical fiber to a nonfiber optical device connector
Patent
1989-11-02
1991-12-24
Lee, John D.
Optical waveguides
With disengagable mechanical connector
Optical fiber to a nonfiber optical device connector
385 33, G02B 642
Patent
active
050746820
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor laser module wherein a semiconductor laser chip and an optical fiber are combined, and a method of positioning the components of such a semiconductor laser module.
2. Description of the Background Art
A single mode optical fiber having a core, the diameter thereof being relatively small (for example, 10 .mu.m), is now widely used as an optical transmission path, since the transmission loss thereof is relatively low and it can be applied to a wide frequency range.
To obtain a long distance transmission by such an optical fiber, an optical beam emitted from a semiconductor laser at an emission angle must be connected to a small incident face of the optical fiber with a high coupling efficiency.
If the laser beam is reflected at the connecting portions of the optical fiber or in optical devices in the optical paths, and if the reflected beam is returned to the semiconductor laser, the oscillation of the laser beam emission becomes unstable and, as a result, noise in the laser beam signal may be increased. Therefore, a semiconductor laser module having an isolation function is required.
Also, the components, such as the semiconductor laser, collimator lens, focussing lens, and the like, including in the semiconductor laser module, must be precisely positioned relative to each other, so that a laser beam emitted from the semiconductor laser is introduced to the optical fiber with a high coupling efficiency.
In the prior art, a known semiconductor laser module comprises: a semiconductor laser chip for emitting a laser beam, a collimator lens for collimating the laser beam to a collimated beam, a focussing lens for focussing the collimated beam, and an optical fiber having an inclined input face to which the laser beam from the focussing lens is input. Such an inclined input face of the optical fiber is advantageous for preventing a return of the laser beam reflected at the input face to the semiconductor laser.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a semiconductor laser module and a method of positioning the components thereof, in which, even if a laser beam emitted from a semiconductor laser chip is reflected at the input face, the reflected light beam is prevented from returning to the semiconductor laser chip.
Another object of the present invention is to provide a semiconductor laser module and a method of positioning the components thereof, in which the positions of these components, such as a semiconductor laser chip, a collimator lens, a focussing lens, and an optical fiber are easily and precisely adjusted and fixed relative to each other.
According to the present invention, there is provided a semiconductor laser module comprising: a semiconductor laser chip for emitting a laser beam; a collimator lens for collimator the laser beam to a collimated beam; a focussing lens having a center axis for focussing the collimated beam; and an optical fiber having an optical axis and an inclined input end face to which the laser beam from the focussing lens is input, characterized in that the focussing lens is arranged in such a manner that the collimated beam incident to the focussing lens has an optical axis deviated from the center axis of the focussing lens, and the optical fiber is arranged in parallel to the collimated beam in such a manner that the laser beam is incident on the optical fiber along the optical axis thereof.
In an embodiment of this invention, the focussing lens comprises a first lens having a center axis thereof and a second lens having a center axis thereof; the collimated beam from the collimator lens is incident on the first lens in such a manner that an optical axis of the laser beam emitted therefrom is in parallel to the center axis of the first lens; and the laser beam incident on the second lens is refracted therein in such a manner that the laser beam output from the second lens is incident on the optical fiber along the optical axis thereof.
In anot
REFERENCES:
patent: 3617129 (1971-11-01), Skolnick
patent: 4790618 (1988-12-01), Abe
patent: 4803689 (1989-02-01), Shibanuma
patent: 4836635 (1989-06-01), De Amorim
patent: 4981335 (1991-01-01), Gaebe
Masuko Takayuki
Moriya Kaoru
Siga Masayuki
Uno Saburo
Fujitsu Limited
Lee John D.
Ngo John
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