Optical inverter and logic devices using same with buffer limite

Details Optical inverter and logic devices using same with buffer limite Optical inverter and logic devices using same with buffer limite

1987-01-12

1989-03-07

Wan, Gene

350 9611, G02B 612

Patent

active

048100501

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a optical logic devices and assemblies for carrying out a logic function on an incident optical signal.
2. Description of the Related Art
Optical logic is most often proposed using active optical components such as bistable devices using laser diodes and photodiodes, laser amplifiers operating with feedback to achieve bistability, self electro-optic effect devices (SEED), holograms and liquid crystal light valves. Some optical logic devices have included waveguides which have a non-linear refractive index so that an incoming light signal switches between output paths in accordance with the intensity of the signal.
The main problems with these devices are their complexity and in some cases the need for feedback. Also, it is not easy to monitor the optical signals.


SUMMARY OF THE INVENTION

In accordance with the present invention, an optical logic device comprises a source of substantially constant optical power; optical signal output means to which the optical power is fed, the optical signal output means having at least one output port and being responsive to electrical control signals selectively to generate optical signals on its at least one output port; optical signal input means to which an incoming optical signal is fed; and detection means for detecting the sense of a change in an optical signal fed to the optical signal input means and for generating a corresponding electrical control signal for controlling the optical signal output means, whereby the optical condition of the at least one output port is changed in the opposite sense.
This logic device is based on the principle of providing an electronic interface between the incoming optical signals and the outgoing optical signals. This means that no optical feedback is required and enables very fast component parts to be used. Potentially, very high speeds may be obtained, possibly of the order of a few tens of pico seconds. The power consumption of the device may be only a few tens of mW at several GBit/s operating speeds. This should be compared with commercial ECL which has typical power dissipation per gate of about 50 mW but at only a few hundred MBits/s.
A further advantage of the invention is that the optical power generation is remote from the other components of the device and thus the total dissipation is simply that of the detection means since in practice the dissipation of the optical signal output means will be negligible. Also, the operation of the device is not dependant upon the optical source wavelength to any marked degree. However, it is preferable if the source generates an incoherent optical beam so that destructive interference does not occur at the optical signal output means.
The logical value of the input optical signal and the output optical signal will be determined by external factors. In the simplest case, the presence of an optical signal may represent one logical condition while the absence of an optical signal may represent the complementary logical condition. Alternatively, a non-zero threshold may be set so that optical signals having an intensity greater than the threshold will represent one logical condition while optical signals having an intensity equal to or less than the threshold will represent the complementary condition. Furthermore, different definitions can be used for the input signals and the output signals.
Monitoring of the high speed optical signals may be achieved by fabricating low coupling ratio directional couplers in the optical paths where required. Such monitoring will not substantially compromise the logic circuit performance in contrast to what may occur with electronic logic at very high speed.
Preferably, the optical signal output means has two output ports, the optical conditions of the output ports being changed in opposite senses in response to the same electrical control signals.
This is particularly advantageous since the device will then produce logically complementary outputs automatically.
Prefer

REFERENCES:
patent: 2936380 (1960-05-01), Anderson
patent: 3781081 (1973-12-01), Rokos
Taylor, "Electro-Optic Technique for Adding Binary Numbers", Elect: Letts, Jul. 24, 1975, vol. 11, No. 15, pp. 313-314.
Neyer et al., "Non Linear Electrooptical Oscillator Using an Integrated Interferometor", Sixth European Conference, Sep. 16-19, 1980, pp. 276-280.

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