EP0524758A2
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EP
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Distortion compensation for analog optical systems
Assignee: AT&T Inc
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Filing: 1992-07-14
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Granted: —
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Expires: 2012-07-14
Abstract
Abstract A distortion arrangement for analog optical communication systems is disclosed which is capable of compensating for system-level distortion attributable to a number of factors including, but not limited to, frequency-dependent transmitting device characteristics, transmission fiber dispersion, doped fiber amplifier gain variations. The distortion arrangement includes a distortion signal path (36) which is configured to characterize the total system nonlinearity, utilizing for example a harmonic generator (38), derivative generator (48), attenuating means (adjustable) (44,50) and time delay means (adjustable) (46,52). The distortion arrangement may be co-located with an optical transmitter and defined as a predistortion arrangement or, conversely, co-located with an optical receiver and defined as a postdistortion arrangement. In general, both a predistorter and postdistorter may be utilized.
Inventors
- 👤 Ernest Eisenhardt Bergmann
- 👤 Chien-Yu Kuo
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 20:52
CPC Classifications
H; H04; H04B; H04B10/00; H04B10/25; H04B10/2507; H04B10/2513; H04B10/25133; H04B2210/00; H04B2210/25; H04B2210/252
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
139 words
In an analog optical communication system, a distortion arrangement for compensating nonlinearities associated with said communication system, said predistortion arrangement comprising splitting means (12), responsive to an input signal (i(t)), for dividing the input signal between a message signal path (14) and a distortion signal path (16); compensation means (18) disposed along the distortion signal path for characterizing system nonlinearities and generating a corrective signal comparable to the distortion associated with said communication system; attenuating means (20) for modifying the relative magnitudes of the signals along the message and distortion signal paths; time delay means (22) for aligning the phase of the signal along the message signal path with the phase of the signal along the distortion signal path; and combining means (24) for adding the phase adjusted output signals to form the output signal of the distortion arrangement.
Claim 2
Dependent Claim
30 words
In an analog optical communication system, a distortion arrangement as defined in claim 1 wherein the distortion arrangement is located with an optical transmitter and defined as a predistortion arrangement.
Claim 3
Dependent Claim
30 words
In an analog optical communication system, a distortion arrangement as defined in claim 1 wherein the distortion arrangement is located with an optical receiver and defined as a postdistortion arrangement.
Claim 4
Dependent Claim
20 words
In an analog optical communication system, a distortion arrangement as defined in claim 1 wherein the attenuating means is adjustable.
Claim 5
Dependent Claim
21 words
In an analog optical communication system, a distortion arrangement as defined in claim 1 wherein the time delay means is adjustable.
Claim 6
Dependent Claim
30 words
In an analog optical communication system, a distortion arrangement as defined in claim 1 wherein the attenuating means and the time delay means are disposed along the message signal path.
Claim 7
Dependent Claim
60 words
In an analog optical communication system, a distortion arrangement as defined in claims 1,4 or 5 wherein the copensation means comprises harmonic generation means responsive to the input modulation signal for forming a k-th power thereof; attenuating means responsive to the output of the harmonic generation means; and time delay means responsive to the output of the harmonic generation means.
Claim 8
Dependent Claim
40 words
In an analog optical communication system, a distortion arrangement as defined in claim 7 wherein the harmonic generation means forms a second harmonic version of the input signal capable of compensating for second order distortion within the analog communication system.
Claim 9
Dependent Claim
40 words
In an analog optical communication system, a distortion arrangement as defined in claims 1,4 or 5 wherein the arrangement further comprises inverting means disposed along the distortion signal path for changing the sign of the magnitude of the distortion signal.
Claim 10
Dependent Claim
73 words
In an analog optical communication system, a distortion arrangement as defined in claims 1,4 or 5 wherein the compensation means comprises harmonic generation means responsive to the input signal for forming a k-th harmonic version thereof; differentiating means responsive to the output of the harmonic generator for forming the j-th derivative thereof; attenuating means responsive to the output of the differentiating means; and time delay responsive to the output of the differentiating means.
Claim 11
Dependent Claim
149 words
In an analog optical communication system, a distortion arrangement as defined in claims 1,4 or 5 wherein the compensation means comprises harmonic generation means responsive to the input signal for forming a k-th power thereof; first attenuating means responsive to the output of the harmonic generation means; first time delay means responsive to the output of the first attenuating means for generating a first distortion output signal; derivative means responsive to the output of the harmonic generation means for forming the j-th derivative of the harmonic signal; second attenuating means responsive to the output of the derivative means; second time delay means responsive to the output of the second attenuating means for generating a second distortion output signal; and combining means for adding the output signals from the message signal path, first distortion signal path and second distortion signal path to form the output signal of the distortion arrangement.
Claim 12
Dependent Claim
33 words
In an analog optical communication system, a distortion arrangement as defined in claim 11 wherein any combination of first and second attenuating means and the first and second time delay means are adjustable.
Claim 13
Dependent Claim
40 words
In an analog optical communication system as defined in claims 11 or 12 wherein the optical communication system comprises an amplitude modulated CATV system, a distortion arrangement wherein the harmonic generation means utilizes k=2 to form a second harmonic signal.
Claim 14
Dependent Claim
82 words
In an analog optical communication system, a distortion arrangement as defined in claim 1,4 or 5 wherein the arrangement further comprises frequency compensating means including frequency predistortion means, configured to model the frequency-dependent input characteristic of an optical transmitting device, the frequency predistortion means disposed at the input to the compensation means; and fequency compensation means disposed at the output of the compensation means, the frequency compensating means configured to essentially cancel the frequency-dependent response at the input of the optical device.
Claim 15
Dependent Claim
155 words
In an analog optical communication system, a distortion arrangement as defined in claims 1,4 or 5 wherein the arrangement further comprises a postdistortion unit located with an optical receiving device, said postdistortion unit postdistortion unit located with an optical receiving device, said postdistortion unit comprising splitting means, responsive to an input signal, for dividing the input signal between a message signal path and a distortion signal path; compensation means disposed along the distortion signal path for characterizing system nonlinearities and generating a corrective signal comparable to the distortion associated with said communication system; attenuating means for modifying the relative magnitudes of the signals along the message and distortion signal paths; time delay means for aligning the phase of the signal along the message signal path with the phase of the signal along the distortion signal path; and combining means for adding the phase adjusted output signals to form the output signal of said postdistortion unit.
Claim 16
Independent Claim
92 words
A method of forming a distortion compensation signal for an analog optical transmission system, the method comprising the steps of: a) splitting an input modulation signal between a message signal path and a distortion signal path; b) forming a k-th harmonic of the signal on the distortion signal path; c) attenuating the magnitude of the signal formed in step b); d) delaying in time the signal formed in step c); and e) combining the signal on the message signal path with the signal formed instep d) to form a distortion compensation signal.
Claim 17
Dependent Claim
23 words
The method according to claim 16 wherein in performing step b), the second harmonic is formed to compensate for composite second order distortion.
Claim 18
Dependent Claim
15 words
The method according to claim 16 wherein in performing step c), the attenuation is adjustable.
Claim 19
Dependent Claim
16 words
The method according to claim 16 wherein in performing step d), the time delay is adjustable.
Claim 20
Dependent Claim
63 words
The method according to claim 16 wherein the method comprises the further steps of: f) forming a j-th derivative of the signal formed in step b); g) attenuating the magnitude of the signal formed in step f); h) delaying in time the signal formed in step g); and i) combining the signal formed in step h) with the combined signals of step e).
Claim 21
Dependent Claim
15 words
The method according to claim 20 wherein in performing step g), the attenuation is adjustable.
Claim 22
Dependent Claim
16 words
The method according to claim 20 wherein in performing step h), the time delay is adjustable.
References Cited (Backward Citations)
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