Optical waveguides – With optical coupler – Input/output coupler
Patent
1996-09-27
1998-06-30
Palmer, Phan T. H.
Optical waveguides
With optical coupler
Input/output coupler
385 34, 385 35, G02B 632
Patent
active
057746079
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a lensed-fiber.
BACKGROUND ART
Coupling an optical semiconductor device, such as a laser diode, and an optical fiber with a high coupling efficiency is one of the most important techniques in the field of light communication. Conventionally known are methods in which the optical semiconductor device and the optical fiber are coupled by means of a lens, such as a spherical or nonspherical lens, located between them, and in which a laser diode 5 is coupled with a hemispherically-ended fiber 1 having a spherical tip end along with a core 1a, as shown in FIG. 7.
In the method in which the laser diode 5 is coupled with the hemispherically-ended fiber 1, no lens is used, so that a small-scale coupling can be enjoyed. In addition, a laser diode array and a hemispherically-ended fiber array can be coupled with each other.
According to this coupling method, however, the distance between the tip end of the hemispherically-ended fiber 1 and an emission end face 5a of the laser diode 5 in the optical axis direction, that is, a working distance, must be adjusted to approximately 10 .mu.m, in order to effectuate a high coupling efficiency. In assembling the hemispherically-ended fiber 1 and the laser diode 5 into a coupling system, therefore, they sometimes come into contact or collision with each other to be damaged and disabled.
Accordingly, a lensed-fiber 2 shown in FIG. 8 has been proposed as coupling means which can solve the above problem. This fiber 2 is coreless and has an isotropic refractive index, and includes a coreless fiber 4 having a spherical tip end, which is connected to the tip end of an optical fiber 3. A working distance D is lengthened so that contact or collision with the laser diode 5 can be avoided.
In the lensed-fiber 2 with the aforesaid construction, however, the tip end of the coreless fiber 4 is spherical in shape, so that there is a problem that the efficiency of coupling with the laser diode 5 is lowered due to spherical aberration. More specifically, light beams emitted from the laser diode 5 are projected at various angles on the spherical surface of the tip end of the coreless fiber 4, theoretically converged by the lens effect of the spherical surface, and projected on a junction surface F.sub.c between the optical fiber 3 and the coreless fiber 4.
There is a problem, however, that some light beams may be incident upon a cladding outside a core 3a on the junction surface F.sub.c between the optical fiber 3 and the coreless fiber 4, or fail to propagate through the core 3a because the angle of incidence is greater than the critical angle even though the core 3a is reached, so that the efficiency of coupling between the lensed-fiber 2 and the laser diode 5 is lowered.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a lensed-fiber which ensures improvement of the efficiency of coupling with an optical semiconductor device.
In order to achieve the above object, the inventors hereof first modeled an analysis of structural parameters of the conventional lensed-fiber 2, which define coupling characteristics for a high coupling efficiency, by a-method based on geometrical optics.
For the conventional lensed-fiber 2, as shown in FIG. 8, the relation between the incidence angle .phi..sub.1 (degrees) of the light beams on the junction surface F.sub.c between the optical fiber 3 and the coreless fiber 4 and the incidence position h.sub.1 (.mu.m) measured from an optical axis L.sub.a was analyzed in a manner such that the emission angle .theta. (degrees) of the light beams from the laser diode 5 as a parameter, was varied by degrees. In this analysis, the lensed-fiber 2 was arranged so that the refractive index of the coreless fiber 4 was 1.45, working distance D was 130, 150, and 170 (.mu.m), length L of the coreless fiber 4 was 1 (mm), and curvature radius R was 75 (.mu.m). FIG. 9 shows the results of this analysis.
In FIG. 9, a black spot represents an analytic value for the incidence angle .phi..sub.1 and the in
REFERENCES:
patent: 4078852 (1978-03-01), Lebduska
patent: 4456330 (1984-06-01), Bludaii
patent: 5293438 (1994-03-01), Konno et al.
patent: 5446816 (1995-08-01), Shiraishi et al.
"A Fiber Lens with a Long Working Distance for Integrated Coupling Between Laser Diodes and Single-Mode Fibers", Journal Of Lightwave Technology, vol. 13, No. 8, Aug. 1995, pp. 1736-1744.
Matsumura Kazuhito
Ohishi Isamu
Shiraishi Kazuo
Palmer Phan T. H.
The Furukawa Electric Co. Ltd.
LandOfFree
Lensed-fiber with cascaded graded-index fiber chip configuration does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lensed-fiber with cascaded graded-index fiber chip configuration, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lensed-fiber with cascaded graded-index fiber chip configuration will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1868957