EP0445978A2
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EP
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Optical communication system with reduced distortion
Assignee: Motorola Solutions Inc
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Filing: 1991-03-01
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Granted: —
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Expires: 2011-03-01
Abstract
Abstract An amplitude modulated optical signaling system (10) having improved linearity and reduced distortion is provided by detecting a portion of the optical output (22) from the light emitter (20) to obtain an electrical feedback signal (32) and phase reversing a first portion of the feedback signal (32R) and degeneratively combining it with the electrical input signal (14) of the system (10) to obtain a combined signal (48) for ac modulating the light emitter (20). A second portion (59) of the feedback signal (32) is desirably time averaged and used to control the dc drive to the light emitter (20) so that the average light output (22) is substantially constant. The distortion otherwise introduced into the optical signaling system (10) by the non-linearity associated with optical emitters (20) driven at high power levels is reduced.
Inventors
- 👤 Henry L. Pfizenmayer
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 19:36
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/50; H04B10/501; H04B10/503; H04B10/504; H04B10/25; H04B10/2507; H04B10/505; H04B10/5057; H04B10/50572; H04B10/516; H04B10/54; H04B10/541; H04B10/58; H01; H01S; H01S5/00; H01S5/06; H01S5/068; H01S5/0683; H01S5/06832
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
163 words
An optical signaling system (10) characterized by: electrically modulatable light emitting means (20) for producing light output (22), modulator means (12) for electrically modulating the light emitting means (20) in response to one or more electrical input signals (14) and one or more feedback signals (32), means (24) for directing a first portion (26) of the light output (22) to a predetermined first signal destination and directing a second portion (28) of the light output (22) to an optical receiver (30) having an electrical output (32) related to the light output (22), wherein the modulator means (12) is characterized by an electrical signal conditioning means (31,33) for treating the electrical output (32) of the optical receiver (30) to derive a feedback signal (32) proportional to the electrical input signal (14) plus distortion products formed within the signaling system (10) which, when combined with the input signal (14) for modulating the light emitting means (20), improves the linearity of the optical signaling system (10).
Claim 2
Dependent Claim
51 words
The system of claim 1 wherein the feedback signal (32) further is characterized by a first feedback signal (48) having an upper frequency at least equal the input (14) signal frequency and a second feedback signal (59) proportional to the average light optical output (22) of the light emitting means (20).
Claim 3
Dependent Claim
30 words
The system of claim 2 wherein the second feedback signal (59) is time averaged over a time interval at least ten times a period of the electrical input signal (14).
Claim 4
Dependent Claim
28 words
The system of claim 2 wherein the signal conditioning means is characterized by means (46) for combining the first feedback signal (48) with the electrical input signal (14).
Claim 5
Dependent Claim
53 words
The system of claim 4 wherein the signal conditioning means further is characterized by means for subtracting first feedback signal (32) from the input electrical signal (14) or vice versa, to provide an combined signal (48) proportional at least in part to distortion products generated within the system (10) but of opposite phase.
Claim 6
Dependent Claim
20 words
The system of claim 1 wherein the optical receiver (30) is characterized by a light sensitive PN junction device (31).
Claim 7
Independent Claim
145 words
A method for reducing distortion in an optical signaling system (10) characterized by: modulating a light emitting means (20) to provide an optical output (22) therefrom; directing a first portion (26) of the optical output (22) to a predetermined signal destination and a second portion (28) to an optical detector (31); in the optical detector (31), converting the second portion (28) of the optical output (22) to an electrical feedback signal (32) containing a combination of input signal (14) information plus distortion generated within the light emitting means (20); inverting the phase and adjusting the amplitude of a first portion (32R) of the electrical feedback signal (32); and degeneratively combining the first portion (32R) of the feedback signal (32) with an input signal (14) desired to be transmitted to the signal destination, to provide a combined signal (48) for modulating the light emitting means (22).
Claim 8
Dependent Claim
29 words
The method of claim 7 further using a second portion of the electrical feedback signal (32) to derive a control signal (59) proportional to the average light output (22).
Claim 9
Dependent Claim
37 words
The method of claim 8 further characterized by using the control signal (59) to adjust the the average light output (22) so as to hold the average light output (22) substantially at a predetermined value or values.
Claim 10
Dependent Claim
40 words
The method of claim 9 wherein the control signal (59) is derived by averaging the second portion of the electrical feedback signal (32) over a time interval which is at least ten times a period of the input signal (14).
References Cited (Backward Citations)
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