Optical quantizing unit and optical A/D converter

Abstract

An optical quantizing unit includes an optical divider dividing 1st optical pulses to be quantized and sending the divided 1st optical pulses into a plurality of paths; a plurality of optical filters passing with different transmittances the divided 1st optical pulses; and an optical threshold filter sequentially receiving the 1st optical pulses, and sending 2nd optical pulses when light intensities of the 1st optical pulses are above a preset threshold value.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a block diagram of an optical A/D converter according to a first embodiment of the invention.

FIG. 2A, FIG. 2B, FIG. 2C and FIG. 2D show waveforms which are processed by the optical A/D converter of FIG. 1.

FIG. 3 is a block diagram of an optical quantizing unit in the optical A/D converter of FIG. 1.

FIG. 4 is a graph showing the relationship between the intensities of input pulses and the number of output pulses in the optical quantizing unit of FIG. 3.

FIG. 5 is a block diagram of an optical threshold filter of the optical quantizing unit of FIG. 3.

FIG. 6 schematically shows an optical threshold filter using bistable semiconductor lasers according to a further embodiment of the invention.

FIG. 7 schematically shows an optical threshold filter using a nonlinear etalon.

FIG. 8 schematically shows an example of an optical quantizing unit which is integrated using a optical waveguide.

Claims

1. An optical quantizing unit comprising: an optical divider dividing 1st optical pulses to be quantized and sending the divided 1st optical pulses to a plurality of paths;a plurality of optical filters passing with different transmittances the divided 1st optical pulses; andan optical threshold filter sequentially receiving the 1st optical pulses, and sending 2nd optical pulses when light intensities of the 1st optical pulses are above a preset threshold value.

2. The optical quantizing unit of claim 1, wherein the optical divider divides the 1st optical pulses, in accordance with the number of quantizing levels.

3. The optical quantizing unit of claim 1 further comprising a plurality of delay units which delay the 1st divided optical pulses, by different times.

4. The optical quantizing unit of claim 1 further comprising an optical synthesizer which sequentially sends the optical threshold filter the 1st optical pulses which have passed through the optical filters.

5. The optical quantizing unit of claim 1, wherein the optical threshold filter includes laser oscillators.

6. The optical quantizing unit of claim 1, wherein the optical threshold filter includes a first laser oscillator whose laser output is reduced in response to the 1st optical pulses which arrive from the optical filters, and a second laser oscillator which receives the laser output from the first laser oscillator, and starts oscillation in response to the reduction of the laser output, the optical threshold filter sending a laser output for the second laser oscillator.

7. The optical quantizing unit of claim 6, wherein the first and second laser oscillators respectively include semiconductor optical amplifiers.

8. The optical quantizing unit of claim 1, wherein the optical threshold filter is a bistable semiconductor laser having a saturable absorber.

9. The optical quantizing unit of claim 1, wherein the optical threshold filter is a resonator constituted by a nonlinear media sandwiched by multilayer mirrors.

10. An optical A/D converter comprising: an optical sampling unit which samples optical analog signals;an optical quantizing unit which quantizes the sampled optical analog signals and outputs the quantized optical pulses; anda binary converter which performs binary conversion of the quantized optical pulses,wherein the optical quantizing unit includes an optical divider which divides 1st optical pulses to be quantized and transmits the divided 1st optical pulses to a plurality of paths; a plurality of optical filters which transmit with different transmittances the divided 1st optical pulses; and an optical threshold filter which sequentially receives the 1st optical pulses from the optical filters, and outputs the quantized 2nd optical pulses when light intensities of the 1st optical pulses are above a preset threshold value.