Optical waveguides – Having nonlinear property
Reexamination Certificate
1999-07-26
2001-08-07
Healy, Brian (Department: 2874)
Optical waveguides
Having nonlinear property
C385S031000, C385S038000, C385S039000, C385S088000, C359S199200, C359S199200, C359S199200, C359S199200
Reexamination Certificate
active
06272274
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an optical transmitting and receiving system for use in bi-directional transmission in a common transmission medium. In the present context, a common transmission medium refers to the common volume of any suitable medium, such as air, space or an optical fibre which is used to transmit optical signals in opposite directions at the same time.
BACKGROUND ART
In many optical applications, it is desirable to utilise the same optical path for signals travelling in opposite directions. The advantages that flow from this configuration include a reduction in the amount of optical alignment required, and where the path is through a dedicated medium such as an optical fibre, a reduction in the amount of medium required.
Prior attempts to achieve bi-directional transmission of optical signals, have utilised laser sources operating through partially reflective mirrors or, in the case of transmission through optical fibres, directional couplers. In both cases, the losses incurred by the use of the partially reflective mirrors and the directional couplers respectively have lowered the efficiency of operation.
DISCLOSURE OF THE INVENTION
It is an object of this invention to provide an improved optical transmitting and receiving system and an improved method for bi-directional transmission of optical signals in a common transmission medium.
Accordingly, the present invention provides an optical transmitting and receiving system for a bi-directional transmission system using a common transmission medium, said transmitting and receiving system including a source of a laser radiation of a first wavelength and intensity, non-linear means responsive to radiation at said first wavelength and intensity to emit radiation of a second wavelength, said non-linear means transmitting incident radiation of said second wavelength having less than a selected intensity, selective reflecting means interposed between said source and said non-linear means to pass radiation of said first wavelength from said source and reflect toward a target radiation of said second wavelength passing through the non-linear means and travelling in the opposite direction to radiation from said source.
Preferably, the non-linear means is an optical parametric oscillator (OPO). The active material of such an oscillator can be chosen to have a threshold intensity for incoming radiation below which conversion to the other wavelength will essentially not occur.
The optical transmitting and receiving system of this invention has particular application to fibre optic communications systems. The radiation generated by the non-linear means at the second frequency is launched into an optical fibre. At the other end of a typical fibre, the signal will be much weaker and the intensity will be less than the chosen operating threshold of the non-linear device. The signal will thus pass through the non-linear device and be reflected to the detector.
Preferably, the selective reflecting means includes a dichroic mirror which reflects radiation of the second wavelength to a target in the form of a suitable detector.
The optical transmitting and receiving system also preferably further includes means to launch the radiation of said second wavelength emitted by the non-linear means for transmission through a medium to a like optical transmitting and receiving system, and means to direct an optical signal from said like optical transmitting and receiving system through said non-linear means to said reflecting means.
The medium used for transmission can be any suitable propagating medium such as air, space or an optical fibre. Where required, adjustable attenuation can be provided for the radiation of said second wavelength emitted from said non-linear means to allow the intensity level of the optical signal reaching the like optical transmitting and receiving system to be reduced below said selected intensity.
Preferably, the laser source is a Nd:YAG laser operating at 1.06 &mgr;m. The non-linear means preferably converts the laser emission to 1.54 &mgr;m. In this form, the invention allows free space laser communications at the eye safe frequency of 1.54 &mgr;m, operating bi-directionally in the same space. This has the significant advantage of avoiding the need for alignment of multiple optical apertures.
REFERENCES:
patent: 5291503 (1994-03-01), Geiger et al.
patent: 5416624 (1995-05-01), Karstensen
patent: 5487124 (1996-01-01), Bowen et al.
patent: 5636232 (1997-06-01), Goto
patent: 5640405 (1997-06-01), Wallace et al.
patent: 5664035 (1997-09-01), Tsuji et al.
patent: 5841798 (1998-11-01), Chen et al.
patent: 5841801 (1998-11-01), Suzuki
G. Bickel et al., “Bidirectional Coupler for Full Duplex Transmission on a Single Optical Fiber”, SPIE vol. 139, 1978, pp. 63-69.
Electro Optic Systems PTY LIM
Healy Brian
Knobbe Martens Olson & Bear LLP
LandOfFree
Optical transmitting and receiving system 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 transmitting and receiving system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical transmitting and receiving system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2478145