1. Field of the Invention
The present invention relates to an optical coupling device; and, more particularly, to an optical coupling device having a silicon optical bench (SiOB) and an optical fiber with an angled end face.
2. Description of Related Arts
As a high-speed Internet network is widely distributed and subscribers to this high-speed Internet network service rapidly increase, the amounts of data traffic also increase. Thus, a telecommunication system that uses electric signals confronts a limitation to meet the above demand. For this reason, an optical communication system is started to be the alternative of the conventional telecommunication system since it is able to transmit large amounts of data. Optical fibers, optical transmitter modules and optical receiver modules are representative optical components used in the optical communication system. For the optical transmitter and receiver modules high-speed, small size, low cost, and an ease of mass-production are key factors in the view of commercialization.
Since a typical optical module using a TO-can packaged optical device has problems in a high-speed operation and a large volume, an optical module using a silicon optical bench (hereinafter referred as to SiOB) technology has been currently developed and commercialized. Herein, the SiOB provide a function for an optical coupling of an optical fiber to a laser by including solder-bumps and a V-shaped groove. A laser chip is aligned and mounted on the SiOB. The V-shaped groove is the place in which an optical fiber is aligned and fixed, and the solder bumps are used for alignment and bonding of a laser chip.
Optical modules using the SiOB have advantages of reduced assembly costs because the optical fiber and the optical active elements such as a laser diode and a photodiode can be aligned by a passive alignment technique such as a conventional flip-chip bonding technique. Also, the optical modules can be minimized due to the fact that plural of optical fiber and arrayed optical active elements can be integrated onto one substrate. FIG. 1 is a diagram showing an optical coupling device using an edge emitting laser and a SiOB structure in accordance with a prior art. (Refer to references G. C. Joo, S. H. Lee, K. S. Park, N. Hwang, J. S. Choi and M. K. Song, “Bidirectional optical coupling of transceiver chip for subscribers”, Electron. Lett., vol. 34, no. 24, November 1998 and M. H. Choi, H. J. Koh, E. S. Yoon, K. C. Shin and K. C. Song, “Self-Aligning Silicon Groove Technology Platform for the Low Cost Optical Module”, IEEE ECTC, pp. 1140–1144, 1999.)
With reference to FIG. 1, a groove 11 is formed on a surface of a SiOB 10. An optical fiber 16 is located on the groove 11. Also, on top of the SiOB 10, a core 17 of the optical fiber 16 is located at a height identical to a height at which an active area of an edge emitting laser 14 is formed. The edge emitting laser 14 is mounted on the SiOB 10 by a metal pad 12 and a solder 13. Typically, a monitoring photodiode 15 is allocated in an opposite to the optical fiber 16.
A light emitted from the edge emitting laser 14 is transmitted 18 through the core 17 of the optical fiber 16 and the monitoring photodiode 15 receives the rear emitted light 19 of the laser 14.
FIG. 2 is a diagram showing an optical coupling device with the use of a surface emitting laser and an optical fiber having an angled end face in accordance with a prior art (Refer to the U.S. Pat. No. 6,389,202 and the U.S. Pat. No. 6,315,464).
With reference to FIG. 2, one end face of an optical fiber 30 to which light is incident is formed as to have an angle of about 45° with respect to an optical fiber axis, and a mirror plane 32 coated with metal such as Au or Al is formed on the angled end face of the optical fiber 30. A vertical cavity surface emitting laser (VCSEL) 33 is allocated at a bottom portion of the angled end face of the optical fiber 30. In this case, a laser light emitted from the VCSEL 33, that is, an incident light IL incident to the optical fiber 30 is reflected at the mirror plane 32 and transmitted through the core 31 of the optical fiber 30. Herein, the light transmitted through the core 31 of the optical fiber 30 is called TL.
However, in the case of applying this optical coupling structure, a reflection light RL is inevitably generated as a portion of the incident light IL emitted from the VCSEL is reflected at end facean incident plane of an optical fiber 30. The reflected light is incident to the VCSEL again. As a result, the VCSEL 33 is degraded due to the reflection light RL.