Optoelectronic circuit

Details Optoelectronic circuit Optoelectronic circuit

1997-12-19

2000-05-09

Palmer, Phan T. H.

Optical waveguides

Integrated optical circuit

385 16, 385 31, 385 37, 385 42, G02B 612

Patent

active

060614811

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to optoelectronic circuits for simultaneous transmitting and receiving operation in a wavelength multiplex process, in a structure in which the relative position of active circuit components determines their operating mode. Single-stage as well as multi-stage circuits with a light waveguide arrangement and light signal detectors and light signal sources as active circuit elements for bidirectional and unidirectional transmitting and receiving operations will be disclosed. The circuits may be structured as integrated or hybrid circuits.
2. Discussion of the Prior Art
A bidirectional optical transmitting and receiving device is known from British patent specification GB-A-2,241,130 provided with an optical duplexer having a waveguide coupling device structured as a quadruple gate. Two gates of the quadruple gate at the same connection side are connected to the active circuit components for transmitting and receiving. The other two gates at the other connection side lead, on the one hand, to an external waveguide and, on the other hand, to a phase shifter. For the reduction of interfering effects between transmitting and receiving components, complementary signals are used which are guided through the actually unnecessary fourth gate and are made available by reflection at a reflecting surface and at the phase shifter.
The state of the art from which the invention is proceeding, is known from Ragdale, C. M., Reid, T. J., Reid D. C. J., Carter, A. C.: Integrated three channel laser and optical multiplexer for narrowband wavelength division multiplexing, Electronics Letters 1994, Vol. 30, No. 11. A wavelength multiplexer is described there which permits unidirectional multi-channel data transmission through a light waveguide. In this respect, the following details are set forth in greater detail:
The wavelength multiplexer is provided with three lasers each of which energizes a transmission channel. The separation between the wavelengths of the lasers, i.e. the channel spacing, amounts to about 5 nm.
The lasers are connected to a signal output by way of several 3 dB couplers, light waveguides and wavelength-selective grating reflectors, at which output the light signals emitted by the lasers are coupled to an external light waveguide. The multiplexer is structured as an optoelectronic integrated circuit, i.e. all structural components are integrated on a chip.
Each 3 dB coupler is connected with four branches of light waveguides, the branches being positioned in opposite pairs. Thus, the first branch and the second branch are arranged opposite the third and fourth branches, respectively.
The first laser of wavelength .lambda..sub.1 is connected to the first branch of the 3 dB coupler. Hence, 50% of the light signals emitted by the first laser are coupled into each of the third and fourth branches of the 3 dB coupler. A wavelength-selective grating reflector reflecting light of wavelength .lambda..sub.1 and being transparent to light of any other wavelength, is arranged in each of the third and fourth branches of the first 3 dB coupler. Thus, the light emitted by the first laser is reflected by the grating reflectors and passes through, or transverses, the coupler again in the opposite direction. The light emitted by the first laser is coupled almost entirely into the second branch to which the signal output of the multiplexer is connected. Since the first 3 dB coupler couples almost the entire light reflected at the grating reflectors into the second branch, not only is interference of the laser by light returning to the first branch prevented but the efficiency during transmission is also improved.
The first laser, the first 3 dB coupler and the first wavelength-selective grating reflector are part of a first stage which energizes the first channel with wavelength .lambda..sub.1. Following this first stage, there is arranged an analogously constructed second stage, the laser of the second stage transmitting light of wavelength .lambda

REFERENCES:
patent: 5825520 (1998-10-01), Huber
Optical Fiber Communication,Summaries of Papers Presented at the Conference OFC, '95, San Diego, Feb. 26-Mar. 3, 1995, vol. 8, 26. Feb. 1995, Institute of Electrical and Electronics Engineers, p. 140, Yamada, Y. et al. "FDM Optical-Loop Buffer and its Applications to a Photonic ATM Switch: Frontier Net" (cited in application).
Ragdale et al.: Integrated Three Channel Laser and Optical Multiplexer for Narrowband Wavelength Division Multiplexing, Electronics Letters 1994, vol. 30, No. 11 (cited in application).

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