Patent
1988-03-23
1990-03-20
Gonzalez, Frank
350 9616, G02B 626
Patent
active
049095846
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to an optical multi/demultiplexer and more particularly, to an optical device such as an optical multiplexer, an optical demultiplexer, an optical multi/demultiplexer, etc., for optical wavelength-division multiplexing transmission of optical fiber communication, and to an optical module produced by integrating these optical devices with semiconductor light emitting and receiving devices.
BACKGROUND ART
Optical wavelength-division multiplexing transmission technique in optical fiber communication is of importance in order to economize a communication system and an optical multi/demultiplexer is an essential device for the optical wavelength-division multiplexing transmission.
Discrete type optical multi/demultiplexers such as an interference filter type and a grating type have been predominant in the past as the structure of the optical multi/demultiplexers. Studies have been made on a waveguide type structure, on the other hand, in order to accomplish a lower cost of production and one-chip monolithic type device. Mention can be made of an optical directional coupler type demultiplexer described in "1978 National Conference On EECE, Paper S6-2" by Sasaki and Ohguro, as an example of such prior art technique. According to this prior art reference, two optical waveguides a and b, each having a width W, are juxtaposed in a length L with a spacing S between them as shown in FIG. 7 of the accompanying drawings. Symbol n.sub.1 represents the refractive index of each optical waveguide and n.sub.2 represents the refractive index of the other portion. This prior art obtains the optical branching characteristics by tilizing the wavelength dependence of coupling of these two optical waveguides. According to this arrangement, two-wavelength multiple light Pi entering from a port 1 is isolated to light P.sub.1 having a wavelength .lambda..sub.1 and light P.sub.2 having a wavelength .lambda..sub.2 and they outgo from ports 2 and 3, respectively. FIG. 8 shows another structure which consists of a plurality of directional couplers 4-1 .about. 4-3 and a plurality of optical multiplexers 5-1 .about. 5-2 in order to improve the isolation characteristics.
DISCLOSURE OF INVENTION
In the optical demultiplexer having the structure shown in FIG. 7, the bandwidth for keeping a transmission loss of at least 25 dB is only about 20 nm when optical branching of wavelength of 1.3 .mu.m and wavelength of 1.55 .mu.m is considered, as represented by wavelength characteristics of FIG. 9. For this reason, if the wavelength values of 1.3 .mu.m and 1.55 .mu.m change due to the temperature change of a semiconductor light emitting device (or semiconductor laser), an optical signal having an undesired wavelength leaks into the system in which the desired wavelength s isolated, so that interference (or so-called "cross-talk") occurs and signal quality deteriorates.
The optical demultiplexer having the structure shown in FIG. 8 can have a large bandwidth for keeping high isolation, but its overall size becomes great because its structural dimension is determined by three mutually different directional couplers and two multiplexers. Accordingly, losses increase due to waveguide loss. Since corresponding masks must be prepared for the directional couplers having mutually different structural dimensions, the cost of production increases. The device cannot be produced easily because the structure is complicated. Particularly because the size is great, at least three exposure masks for patterning are necessary so that the cost of production increases while production accuracy is low and production itself is difficult.
The problem common to FIGS. 7 and 8 is as follows. When an optical module is produced by forming integrally a semiconductor device(s) (a light emitting device or a light receiving device or both) on the side of the ports 2 and 3, the optical module must be replaced as a whole if one or both of the semiconductor optical devices exhibit degradation of quality or get broke, and this is
REFERENCES:
patent: 4341438 (1982-07-01), Seki et al.
Imoto Katsuyuki
Sano Hirohisa
Tsushima Hideaki
Gonzalez Frank
Hitachi , Ltd.
LandOfFree
Optical multi/demultiplexer and optical module using the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical multi/demultiplexer and optical module using the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical multi/demultiplexer and optical module using the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-787969