Optical communications module
First Claim
1. An optical communications module, comprising:
- a transmitting/receiving section which sends a transmitted signal to a transmission path as an optical signal and receives an optical signal from said transmission path; and
a drive section, which applies said transmitted signal to the transmitting/receiving section and reproduces said received optical signal applied from the transmitting/receiving section as a received electrical signal,wherein said transmitting/receiving section includes a laser diode that outputs the optical signal transmitted to the transmission path and a photo diode for monitoring the optical signal output from the laser diode, and said drive section includes a threshold control circuit which controls a bias current of said laser diode so that an optical noise output from said laser diode, which is detected by said photodiode, is maximized, thereby causing the bias current value of the laser diode to be equal to and track a threshold current value.
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Accused Products
Abstract
A compact, low-cost combined transmitting/receiving optical communications module, which is suitable for use in a TCM system and which is capable of normal operation over a particularly wide temperature range in optical communications equipment, is provided. The optical transmitting/receiving section for this purpose has a laser diode which outputs a transmitted optical signal, a combined monitor/receiving photodiode which not only monitors the optical output signal from the laser diode during a transmitting period, but also receives the input optical signal from the transmission path during the receiving period, and an optical mixer/divider which performs transmitting/receiving mixing and dividing between the transmission path, the laser diode, and the photodiode. A drive section has a transmitting/receiving switching circuit which performs time-division transmitting/receiving switching and a threshold control circuit which performs successive control of the bias current of the laser diode so that the optical noise output monitored by the photodiode is maximized.
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Citations
12 Claims
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1. An optical communications module, comprising:
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a transmitting/receiving section which sends a transmitted signal to a transmission path as an optical signal and receives an optical signal from said transmission path; and a drive section, which applies said transmitted signal to the transmitting/receiving section and reproduces said received optical signal applied from the transmitting/receiving section as a received electrical signal, wherein said transmitting/receiving section includes a laser diode that outputs the optical signal transmitted to the transmission path and a photo diode for monitoring the optical signal output from the laser diode, and said drive section includes a threshold control circuit which controls a bias current of said laser diode so that an optical noise output from said laser diode, which is detected by said photodiode, is maximized, thereby causing the bias current value of the laser diode to be equal to and track a threshold current value. - View Dependent Claims (2)
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3. An optical communications module comprising:
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a transmitting/receiving section which sends a transmitted signal to a transmission path as an optical signal and receives an optical signal from said transmission path; and a drive section, which applies said transmitted signal to the transmitting/receiving section and reproduces said receives optical signal applied from the transmitting/receiving section as a received electrical signal, wherein said transmitting/receiving section includes a laser diode that outputs the optical signal transmitted to the transmission path and a photo diode for monitoring the optical signal output from the laser diode, and said drive section includes a threshold control circuit which controls a bias current of said laser diode so that an optical noise output from said laser diode, which is detected by said photodiode, is maximized, thereby causing the bias current of the laser diode to track a threshold current value, an I/V conversion circuit which converts the monitor current from said photodiode to a voltage; an amplifier circuit which amplifies said voltage converted from said optical noise output to a selected level; a bandpass filter which passes components of said transmitted signal which are even multiples of the flock frequency fo; a detection circuit which outputs a rectified output of said bandpass filter; a sampling pulse generation circuit which generates a clock for the purpose of sampling the rectified output of said detection circuit; a sampling and hold circuit which samples and holds said rectified output in accordance with the sampling clock from said sampling pulse generation circuit; a comparator which compares the rectified output from said detection circuit with the sampled and held value from the previous clock cycle, from said sample and hold circuit to detect the increase on decrease in said optical noise components; an up/down controllable counter which counts said sampling clock pulses; a counter up/down switching section which uses the output of said comparator to control the up-counting and down-counting of said counter so that said optical noise components are maximized; a D/A converter which performs digital-to-analog conversion of the count output of said counter; a lowness filter which smooths the output of said D/A converter; and a bias current control circuit which controls the bias current of said laser diode in accordance with the output of said lowpass filter. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification