EP0129305A2
Expired / Lapsed
EP
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Optical fibre receiver
Assignee: STC PLC
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Filing: 1984-03-27
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Granted: —
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Expires: 2004-03-27
Abstract
Abstract @ In an optical fibre receiver, the modulated light falls on a p-i-n diode (PD) connected to the input of an operational amplifier (A). This amplifier is shunted by a load resistor (R), which in turn is shunted by a non-linear Schottky diode (SD). This prevents a large pulse from spoiling the sensitivity of the receiver to a following smaller pulse. This also provides the receiver with a low pass response having a relatively long time constant. In addition to this, the a.c. coupling response for the connection to the next stage of the system has a relatively short time constant. These two time constants combine to give an overall characteristic with a relatively narrow bandwidth, which enhances the above effect. Finally, when the line muting function is needed, as between messages, the bit stream as detected includes a double amplitude pulse whose detection initiates the line muting function. This can be implemented by a double length pulse included in the bus bit stream which is so detected as to give a double amplitude pulse.
Inventors
- 👤 David Philip Martin Chown
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-01 23:33
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/60; H04B10/66; H04B10/69; H04B10/697
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
113 words
An optical receiver for the reception of a modulated light beam from an optical pulse transmission line or from free space, which includes a p-i-n diode on to which the modulated light beam is directed to produce therein an electrical current appropriate to the modulated beams, an amplifier to an input of which the diode is connected, the output of the amplifier being coupled to the detecting circuitry of the receiver when in use, a resistive load connected between said input and said output, and a non-linear diode connected in parallel with the resistive load, which diode acts as a dynamic load to prevent saturation of the amplifier under high input signal conditions.
Claim 2
Dependent Claim
113 words
An optical receiver for the reception of a modulated light beam from an optical pulse transmission line or from free space, which includes a p-i-n diode on to which the modulated light beam is directed to produce therein an electrical current appropriate to the modulated beams, an amplifier to an input of which the diode is connected, the output of the amplifier being coupled to the detecting circuitry of the receiver when in use, a resistive load connected between said input and said output, and a non-linear diode connected in parallel with the resistive load, which diode acts as a dynamic load to prevent saturation of the amplifier under high input signal conditions.
Claim 3
Dependent Claim
25 words
A receiver as claimed in claim 1, and in which the amplifier is an operational amplifier, the p-i-n diode being connected to its inverting input.
Claim 4
Dependent Claim
15 words
A receiver as claimed in claim 2, in which the' diode is a Schottky diode.
Claim 5
Dependent Claim
63 words
A receiver as claimed in claim 3, in which the alternating current coupling response for the coupling between the said amplifier and the detection circuitry, and the receiver low-pass response are so related that the curve of the receiver's overall response has a relatively narrow frequency band-width, whereby the receiver's sensitivity is not reduced significantly after the reception of a high amplitude signal.
Claim 6
Dependent Claim
87 words
An optical transmission system in which the or each receiver, or the receiving part of the or each said transceiver is a receiver as claimed in claim 1, in which when an inter-message switching function is required the bit stream includes one or more pulses whose magnitude or duration exceeds the magnitudes or durations of the other pulses.in the bit stream, and in which the or each such receiver includes a threshold detector responsive to a said higher magnitude or duration pulse to initiate the switching functional.
Claim 7
Dependent Claim
68 words
An optical receiver for the reception of a modulated light beam from an optical fibre transmission line or from free space, in which the alternating current coupling response and the receiver low pass response are so related that the curve of the receiver's overall response has a relatively narrow frequency width, whereby the receiver's overall response is not reduced significantly after the reception of a high amplitude signal.
Claim 8
Dependent Claim
68 words
An optical receiver for the reception of a modulated light beam from an optical fibre transmission line or from free space, in which the alternating current coupling response and the receiver low pass response are so related that the curve of the receiver's overall response has a relatively narrow frequency width, whereby the receiver's overall response is not reduced significantly after the reception of a high amplitude signal.
Claim 9
Dependent Claim
155 words
An optical receiver for the reception of a modulated light beam from an optical fibre transmission line or from free space, in which the alternating current coupling response for the coupling of the output of the receiver to subsequent circuit elements is so chosen, by virtue of the parameters of the components used as to have a relatively short time constant, e.g. in the range of 100-140 ns, in which the receiver loss pass response is so chosen by virtue of the components used as to have a relatively long time constant, e.g. in the range of 160 to 180 ns, and in which the combination of said relatively short coupling time constant and said relatively long low pass response time constant ensures that the overall response of the receiver is a relatively narrow overall bandwidth response, so that the receiver's overall response is not reduced significantly after the reception of a high amplitude signal.
Claim 10
Dependent Claim
155 words
An optical receiver for the reception of a modulated light beam from an optical fibre transmission line or from free space, in which the alternating current coupling response for the coupling of the output of the receiver to subsequent circuit elements is so chosen, by virtue of the parameters of the components used as to have a relatively short time constant, e.g. in the range of 100-140 ns, in which the receiver loss pass response is so chosen by virtue of the components used as to have a relatively long time constant, e.g. in the range of 160 to 180 ns, and in which the combination of said relatively short coupling time constant and said relatively long low pass response time constant ensures that the overall response of the receiver is a relatively narrow overall bandwidth response, so that the receiver's overall response is not reduced significantly after the reception of a high amplitude signal.
Claim 11
Dependent Claim
40 words
An optical receiver as claimed in claim 7, and in which the alternating coupling response is defined by a capacitor of 470pF connected to the output of the receiver's input stage, together with a resistor of 270K ohm fed therefrom.
Claim 12
Dependent Claim
42 words
An optical receiver as claimed in claim 8, in which the low pass response of the receiver is defined by a resistor of 500 K ohms connected across said input stage in parallel with a non-linear device such as a Schottky diode.
Claim 13
Dependent Claim
65 words
An optical receiver as claimed in claim 9, in which the input stage includes a field effect transistor (FET) to the gate of which is applied the optical signal, which FET is connected in cascode fashion with the emitter-collector path of a transistor, and in which the collector of said transistor is connected to the base of a further transistor which forms an output amplifier.
Claim 14
Dependent Claim
31 words
An optical receiver as claimed in claim 10, and in which the emitter output of said further transistor is connected via another transistor to two separate amplifiers to give two outputs.
Claim 15
Dependent Claim
57 words
An optical transmission system, in which when the muting function is required the bit stream includes one or more pulses whose magnitude exceeds the magnitudes of the other pulses in the bit stream, and in which the receiver of the system includes a threshold detector responsive to a said higher magnitude pulse to initiate the mute function.
Claim 16
Dependent Claim
57 words
An optical transmission system, in which when the muting function is required the bit stream includes one or more pulses whose magnitude exceeds the magnitudes of the other pulses in the bit stream, and in which the receiver of the system includes a threshold detector responsive to a said higher magnitude pulse to initiate the mute function.
Claim 17
Dependent Claim
34 words
An system as claimed in claim 12, in which the higher magnitude pulse is derived from a longer pulse on detection in the receiver, which longer pulse is included in the bus bit stream.
Claim 18
Dependent Claim
26 words
A system as claimed in claim 13, in which the higher magnitude pulse has an amplitude at least twice that of the smallest expected pulse amplitude.
Claim 19
Dependent Claim
25 words
A system as claimed in claim 14, in which the detection of the longer pulse involves integration or the reliance on a narrow pass band.
References Cited (Backward Citations)
No citation records indexed.
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