CA2213866A1 - Transmitter and method for optically transmitting electric frequency-division multiplex signals - Google Patents
Transmitter and method for optically transmitting electric frequency-division multiplex signalsInfo
- Publication number
- CA2213866A1 CA2213866A1 CA 2213866 CA2213866A CA2213866A1 CA 2213866 A1 CA2213866 A1 CA 2213866A1 CA 2213866 CA2213866 CA 2213866 CA 2213866 A CA2213866 A CA 2213866A CA 2213866 A1 CA2213866 A1 CA 2213866A1
- Authority
- CA
- Canada
- Prior art keywords
- frequency
- division multiplex
- signal
- transmitter
- vor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 238000000034 method Methods 0.000 title claims description 5
- 230000003287 optical effect Effects 0.000 claims abstract description 33
- 230000005540 biological transmission Effects 0.000 claims abstract description 23
- 239000003990 capacitor Substances 0.000 claims description 6
- 230000003247 decreasing effect Effects 0.000 abstract description 7
- 239000002131 composite material Substances 0.000 abstract description 2
- 101710170231 Antimicrobial peptide 2 Proteins 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 239000013307 optical fiber Substances 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 230000001419 dependent effect Effects 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
- H04B10/504—Laser transmitters using direct modulation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/58—Compensation for non-linear transmitter output
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Nonlinear Science (AREA)
- Optics & Photonics (AREA)
- Optical Communication System (AREA)
Abstract
When frequency-division multiplex signals are optically transmitted over an optical transmission line, distortions of the subcarrier signal levels occur, e.g., increasing subcarrier signal levels for increasing frequencies. A frequency-division multiplex signal to be transmitted is fed to a predistortion unit (VOR) which attenuates high frequencies, for example. To this end, the predistortion unit (VOR) comprises, for example, a coil (L) in the series arm, with which subcarrier signal levels decreasing with increasing frequencies are generated. With the value of the coil (L), the characteristic of the decreasing subcarrier signal levels is set inversely proportional to the characteristic of the expected distortions of the subcarrier signal levels on a given optical transmission line. The predistorted composite signals are converted to optical signals by a directly modulated laser diode (LAS), and optically transmitted.
Description
Transmitter and Method for Optically Transmitting Electric Frequency-Division Multiplex Signals This invention relates to a transmitter as set forth in the preamble of claim 1 and to a method as set forth in the preamble of claim 7.
Frequency-division multiplex signals consist of two or more subcarrier signals which are transmitted simultaneously over a common path. The individua subcarrier signals are transmitted in different frequency bands at different carrier frequencies.
During optical transmission of electric frequency-division multiplex signals over an optical transmission line, the individual signal levels vary with frequency. In Journal of Lighwave Technology, Vol. 10, No. 1, January 1992, a small-signal analysis for an optical communication system with a directly modulated laser of wavelength A = 1550 nm, a 30-km-long optical-fiber link, and a receiver is described on pages 96 to 100. In the frequency range used, the frequency response of a frequency-division multiplex signal rises steeply. This, in conjunction with a constant, frequency-independent noise power density in the receiver, results in the dynamic range for low-frequency subcarrier signals being smaller than that for radio-frequency subcarrier signals.
It is therefore an object of the invention to compensate for the variations with frequency resulting during optical transmission of electric frequency-division multiplex signals.
This object is attained by the teachings of claims 1 and 7. Further advantageous features of the invention are defined in dependent claims 2 to 6.
A particular advantage of the invention is that a greater link length can be achieved with unchanged optical output power. Furthermore it is possible to transmit signals with a greater bandwidth. For the same link length and the same bandwidth, the optical output power of the transmitter can be reduced, which permits use of less expensive lasers. In addition, the invention increases the output range of the transmitter, and a greater dynamic range which is constant over frequency achieved in the receivers.
The invention will become more apparent from the following description of two embodiments taken in conjunction with the accompanying drawings, in which:
Fig. 1 is a schematic representation of a transmission system according to the invention for transmitting electric frequency-division multiplex signals;
Fig. 2 shows schematically the construction of a transmitter according to the invention;
Fig. 3 shows schematically the construction of a predistortion unit for the transmitter of of Fig. 2; and Fig. 4 shows two diagrams of two electric frequency-division multiplex signals.
The first embodiment will be described with reference to Figs. 1 and 2. Fig. 1 shows a transmission system SYS for optically transmitting electric frequency-division multiplex signals. The transmission system SYS comprises a transmitter SEN, from which the frequency-division multiplex signals are transmitted over an optical transmission line, e.g., an optical-fiber link, which may contain optical amplifiers, to an optical splitter. The optical transmission line to the optical splitter may be 200 to 500 km long, for example. The frequency-division multiplex signals are divided in the optical splitter, which is a 1:16 splitter, for example, and are transmitted over, e.g., 16, separate optical transmission lines to 16 receivers EMP (only one shown). The separate optical transmission lines are 1 to 20 km long, for example.
Each of the receivers EMP converts the received frequency-division multiplex signals from optical to electrical form, so that they can be transmitted over coaxial cables to several terminals. The transmission system SYS is thus suitable for distributing cable television signals.
Fig. 2 shows the transmitter SEN of Fig. 1 in more detail. The electric frequency-division multiplex signals to be transmitted are provided, for example, by a cable television head end, which receives television signals via a satellite antenna, or by a video server, which holds a plurality of video films that are retrievable via request signals, and are fed to the transmitter SEN.
The transmitter SEN serves to convert the received frequency-division multiplex signals from electrical to optical form and to transmit the optical signals over the optical transmission lines to the receivers EMP. During the transmission of a frequency-division multiplex signal, distortions of the individual subcarrier levels are caused by, e.g., chromatic dispersion. The distortions cause, for example, a subcarrier signal level characteristic rising with increasing frequencies, i.e., an increasing frequency response. The distance between the subcarrier signal levels of the carrier frequencies 0.1 GHz and 1 GHz in the case of a 200-km-long optical-fiber link is, for example, 9 dB.
To compensate for the distortions, the transmitter SEN
includes a predistortion unit VOR. The subcarrier signals of a received electric frequency-division multiplex signal have equal signal levels, i.e., a uniform frequency response. The predistortion unit VOR
generates from this frequency-division multiplex signal a frequency-division multiplex signal with different signal levels. The signal level characteristic will ideally be set inversely proportional to the characteristic of the expected distortions of the signal levels on the optical transmission line. If the distortions cause a signal level characteristic which rises linearly with increasing frequencies, for example, a frequency-division multiplex signal will be generated whose subcarrier signal level characteristic decreases linearly with increasing frequencies. The circuit of the predistortion unit VOR comprises a coil L in the series arm. The impedance of the coil L causes a frequency-division multiplex signal with equal signal levels to be converted to a frequency-division multiplex signal with subcarrier signal levels decreasing with increasing frequencies when passing through the predistortion unit VOR. With the value of the coil L, the subcarrier signal level characteristic is set.
The transmitter SEN further comprises two electric amplifiers AMPl, AMP2 and a directly modulated laser LAS in the form of a laser diode, which serves to convert the predistorted electric frequency-division multiplex signals to optical signals.
The electric amplifier AMPl serves to amplify the received electric frequency-division multiplex signals and feeds the amplified signals to the predistortion unit VOR. The received frequency-division multiplex signals and the amplified signals have respective subcarrier signals with equal signal levels. If the electric amplifier AMP is to serve only as a decoupling element, its gain may also be unity.
The electric amplifier AMP2 receives the frequency-division multiplex signals predistorted in the predistortion unit VOR. It serves to amplify the predistorted frequency-division multiplex signals and feeds the amplified signals to the directly modulated laser LAS. The gain of the amplifier AMP is chosen so that the average input signal power of the directly modulated laser LAS lies in an optimized range dependent on the length of the optical transmission lines. The average power may also be set via the gain of the amplifier AMPl. In that case, the electric amplifier AMP2 serves as a unity-gain decoupling element, for example.
The transmitter SEN thus contains a series combination of amplifier AMPl, predistortion unit VOR, amplfiier AMP2, and directly modulated laser LAS.
The second embodiment will now be described with reference to Fig. 3. Fig. 3 shows a predistortion unit VOR which can be used instead of the predistortion unit in the transmitter of Fig. 2. The predistortion unit VOR of Fig. 3 comprises a capacitor C in the shunt arm. It serves to predistort received and amplified frequency-division multiplex signals in such a way as to compensate for the expected distortions on the optical transmission lines. The impedance of the capacitor C causes a frequency-division multiplex signal with equal subcarrier signal levels to be converted to a frequency-division multiplex signal with subcarrier signal levels decreasing with increasing frequencies when passing through the predistortion unit VOR of Fig. 3. With the value of the capacitor C, the subcarrier signal level characteristic is set.
Finally, a method of optically transmitting electric frequency-division multiplex signals consisting of multiplexed subcarrier signals will be described for the two embodiments with the aid of Fig. 4. Fig. 4a shows an electric frequency-division multiplex signal with equal subcarrier signal levels. The value of the signal level is plotted as a function of frequency, i.e., the diagram shows the frequency response. In this example, the electric frequency-division multiplex signal contains four subcarrier signals with the same signal level P0 at the frequencies fl to f4.
Fig. 4b shows an electric frequency-division multiplex signal with different subcarrier signal levels. The value of the signal level is plotted as a function of frequency. In this example, the composite electric signal contains four subcarrier signals. The first subcarrier signal, at frequency fl, has the signal level P1, the second, at f2, the signal level P2, the third, at f3, the signal level P3, and the fourth, at frequency f4, the signal level P4. The following inequalities hold: P1 > P2 > P3 > P4 and f4 > f3 > f2 > fl.
Each subcarrier signal has a frequency spectrum with the associated useful-information contents, which is not shown in the diagrams of Figs. 4a and 4b to simplify the illustration.
An electric frequency-division multiplex signal as shown in Fig. 4a is transmitted from, for example, a cable television station to a transmitter as shown in Fig. 2. In the transmitter, the frequency-division multiplex signal is amplified by a first amplifier with constant, frequency-independent gain, and fed to a predistortion unit. When passing through the predistortion unit, subcarrier signals of higher frequencies are attenuated more than subcarrier signals of lower frequencies, as shown in Fig. 4b.
Accordingly, the points (fl, P1), (f2, P2), (f3, P3), (f4, P4) form a monotonically decreasing function and, to a first approximation, are located, for example, on a straight line. The slope of the straight line is negative in the case of a subcarrier level characteristic which increases with increasing frequencies. In the case of a subcarrier signal level characteristic decreasing linearly with increasing frequencies due to linear distortion, the slope of the straight line through the points (fl, P1), (f2, P2), (f3, P3), (f4, P4) must be chosen to be positive and its magnitude must be equal to that of the decreasing subcarrier signal level characteristic. In both cases, a compensation for the expected distortions on the optical transmission lines is achieved by the predistortion. The predistorted frequency-division multiplex signal is fed to a second amplifier, which amplifies it in a constant manner, i.e., all signal levels are amplified alike. The gain is chosen so that the average power of the amplified frequency-division multiplex signal is optimized for transmission over the optical transmission lines. The amplified frequency-division multiplex signal is fed to a directly modulated laser which converts it to an optical signal that is transmitted over the optical transmission lines to one or more receivers. Ideally, i.e., with optimum compensation, the receivers receive a frequency-division multiplex signal as shown in Fig.
4a.
Instead of using a single coil or a single capacitor for the predistortion unit, a combination of resistors, coils, and capacitors may be employed. By means of an RLC circuit with adjustable R, L, and/or C values, for example, a distortion of the subcarrier signal levels measured in a receiver can be compensated for in a variable manner even during operation.
Frequency-division multiplex signals consist of two or more subcarrier signals which are transmitted simultaneously over a common path. The individua subcarrier signals are transmitted in different frequency bands at different carrier frequencies.
During optical transmission of electric frequency-division multiplex signals over an optical transmission line, the individual signal levels vary with frequency. In Journal of Lighwave Technology, Vol. 10, No. 1, January 1992, a small-signal analysis for an optical communication system with a directly modulated laser of wavelength A = 1550 nm, a 30-km-long optical-fiber link, and a receiver is described on pages 96 to 100. In the frequency range used, the frequency response of a frequency-division multiplex signal rises steeply. This, in conjunction with a constant, frequency-independent noise power density in the receiver, results in the dynamic range for low-frequency subcarrier signals being smaller than that for radio-frequency subcarrier signals.
It is therefore an object of the invention to compensate for the variations with frequency resulting during optical transmission of electric frequency-division multiplex signals.
This object is attained by the teachings of claims 1 and 7. Further advantageous features of the invention are defined in dependent claims 2 to 6.
A particular advantage of the invention is that a greater link length can be achieved with unchanged optical output power. Furthermore it is possible to transmit signals with a greater bandwidth. For the same link length and the same bandwidth, the optical output power of the transmitter can be reduced, which permits use of less expensive lasers. In addition, the invention increases the output range of the transmitter, and a greater dynamic range which is constant over frequency achieved in the receivers.
The invention will become more apparent from the following description of two embodiments taken in conjunction with the accompanying drawings, in which:
Fig. 1 is a schematic representation of a transmission system according to the invention for transmitting electric frequency-division multiplex signals;
Fig. 2 shows schematically the construction of a transmitter according to the invention;
Fig. 3 shows schematically the construction of a predistortion unit for the transmitter of of Fig. 2; and Fig. 4 shows two diagrams of two electric frequency-division multiplex signals.
The first embodiment will be described with reference to Figs. 1 and 2. Fig. 1 shows a transmission system SYS for optically transmitting electric frequency-division multiplex signals. The transmission system SYS comprises a transmitter SEN, from which the frequency-division multiplex signals are transmitted over an optical transmission line, e.g., an optical-fiber link, which may contain optical amplifiers, to an optical splitter. The optical transmission line to the optical splitter may be 200 to 500 km long, for example. The frequency-division multiplex signals are divided in the optical splitter, which is a 1:16 splitter, for example, and are transmitted over, e.g., 16, separate optical transmission lines to 16 receivers EMP (only one shown). The separate optical transmission lines are 1 to 20 km long, for example.
Each of the receivers EMP converts the received frequency-division multiplex signals from optical to electrical form, so that they can be transmitted over coaxial cables to several terminals. The transmission system SYS is thus suitable for distributing cable television signals.
Fig. 2 shows the transmitter SEN of Fig. 1 in more detail. The electric frequency-division multiplex signals to be transmitted are provided, for example, by a cable television head end, which receives television signals via a satellite antenna, or by a video server, which holds a plurality of video films that are retrievable via request signals, and are fed to the transmitter SEN.
The transmitter SEN serves to convert the received frequency-division multiplex signals from electrical to optical form and to transmit the optical signals over the optical transmission lines to the receivers EMP. During the transmission of a frequency-division multiplex signal, distortions of the individual subcarrier levels are caused by, e.g., chromatic dispersion. The distortions cause, for example, a subcarrier signal level characteristic rising with increasing frequencies, i.e., an increasing frequency response. The distance between the subcarrier signal levels of the carrier frequencies 0.1 GHz and 1 GHz in the case of a 200-km-long optical-fiber link is, for example, 9 dB.
To compensate for the distortions, the transmitter SEN
includes a predistortion unit VOR. The subcarrier signals of a received electric frequency-division multiplex signal have equal signal levels, i.e., a uniform frequency response. The predistortion unit VOR
generates from this frequency-division multiplex signal a frequency-division multiplex signal with different signal levels. The signal level characteristic will ideally be set inversely proportional to the characteristic of the expected distortions of the signal levels on the optical transmission line. If the distortions cause a signal level characteristic which rises linearly with increasing frequencies, for example, a frequency-division multiplex signal will be generated whose subcarrier signal level characteristic decreases linearly with increasing frequencies. The circuit of the predistortion unit VOR comprises a coil L in the series arm. The impedance of the coil L causes a frequency-division multiplex signal with equal signal levels to be converted to a frequency-division multiplex signal with subcarrier signal levels decreasing with increasing frequencies when passing through the predistortion unit VOR. With the value of the coil L, the subcarrier signal level characteristic is set.
The transmitter SEN further comprises two electric amplifiers AMPl, AMP2 and a directly modulated laser LAS in the form of a laser diode, which serves to convert the predistorted electric frequency-division multiplex signals to optical signals.
The electric amplifier AMPl serves to amplify the received electric frequency-division multiplex signals and feeds the amplified signals to the predistortion unit VOR. The received frequency-division multiplex signals and the amplified signals have respective subcarrier signals with equal signal levels. If the electric amplifier AMP is to serve only as a decoupling element, its gain may also be unity.
The electric amplifier AMP2 receives the frequency-division multiplex signals predistorted in the predistortion unit VOR. It serves to amplify the predistorted frequency-division multiplex signals and feeds the amplified signals to the directly modulated laser LAS. The gain of the amplifier AMP is chosen so that the average input signal power of the directly modulated laser LAS lies in an optimized range dependent on the length of the optical transmission lines. The average power may also be set via the gain of the amplifier AMPl. In that case, the electric amplifier AMP2 serves as a unity-gain decoupling element, for example.
The transmitter SEN thus contains a series combination of amplifier AMPl, predistortion unit VOR, amplfiier AMP2, and directly modulated laser LAS.
The second embodiment will now be described with reference to Fig. 3. Fig. 3 shows a predistortion unit VOR which can be used instead of the predistortion unit in the transmitter of Fig. 2. The predistortion unit VOR of Fig. 3 comprises a capacitor C in the shunt arm. It serves to predistort received and amplified frequency-division multiplex signals in such a way as to compensate for the expected distortions on the optical transmission lines. The impedance of the capacitor C causes a frequency-division multiplex signal with equal subcarrier signal levels to be converted to a frequency-division multiplex signal with subcarrier signal levels decreasing with increasing frequencies when passing through the predistortion unit VOR of Fig. 3. With the value of the capacitor C, the subcarrier signal level characteristic is set.
Finally, a method of optically transmitting electric frequency-division multiplex signals consisting of multiplexed subcarrier signals will be described for the two embodiments with the aid of Fig. 4. Fig. 4a shows an electric frequency-division multiplex signal with equal subcarrier signal levels. The value of the signal level is plotted as a function of frequency, i.e., the diagram shows the frequency response. In this example, the electric frequency-division multiplex signal contains four subcarrier signals with the same signal level P0 at the frequencies fl to f4.
Fig. 4b shows an electric frequency-division multiplex signal with different subcarrier signal levels. The value of the signal level is plotted as a function of frequency. In this example, the composite electric signal contains four subcarrier signals. The first subcarrier signal, at frequency fl, has the signal level P1, the second, at f2, the signal level P2, the third, at f3, the signal level P3, and the fourth, at frequency f4, the signal level P4. The following inequalities hold: P1 > P2 > P3 > P4 and f4 > f3 > f2 > fl.
Each subcarrier signal has a frequency spectrum with the associated useful-information contents, which is not shown in the diagrams of Figs. 4a and 4b to simplify the illustration.
An electric frequency-division multiplex signal as shown in Fig. 4a is transmitted from, for example, a cable television station to a transmitter as shown in Fig. 2. In the transmitter, the frequency-division multiplex signal is amplified by a first amplifier with constant, frequency-independent gain, and fed to a predistortion unit. When passing through the predistortion unit, subcarrier signals of higher frequencies are attenuated more than subcarrier signals of lower frequencies, as shown in Fig. 4b.
Accordingly, the points (fl, P1), (f2, P2), (f3, P3), (f4, P4) form a monotonically decreasing function and, to a first approximation, are located, for example, on a straight line. The slope of the straight line is negative in the case of a subcarrier level characteristic which increases with increasing frequencies. In the case of a subcarrier signal level characteristic decreasing linearly with increasing frequencies due to linear distortion, the slope of the straight line through the points (fl, P1), (f2, P2), (f3, P3), (f4, P4) must be chosen to be positive and its magnitude must be equal to that of the decreasing subcarrier signal level characteristic. In both cases, a compensation for the expected distortions on the optical transmission lines is achieved by the predistortion. The predistorted frequency-division multiplex signal is fed to a second amplifier, which amplifies it in a constant manner, i.e., all signal levels are amplified alike. The gain is chosen so that the average power of the amplified frequency-division multiplex signal is optimized for transmission over the optical transmission lines. The amplified frequency-division multiplex signal is fed to a directly modulated laser which converts it to an optical signal that is transmitted over the optical transmission lines to one or more receivers. Ideally, i.e., with optimum compensation, the receivers receive a frequency-division multiplex signal as shown in Fig.
4a.
Instead of using a single coil or a single capacitor for the predistortion unit, a combination of resistors, coils, and capacitors may be employed. By means of an RLC circuit with adjustable R, L, and/or C values, for example, a distortion of the subcarrier signal levels measured in a receiver can be compensated for in a variable manner even during operation.
Claims (7)
1. A transmitter (SEN) for optically transmitting an electric frequency-division multiplex signal consisting of multiplexed subcarrier signals with equal signal levels, comprising a directly modulated laser (LAS) for converting the electric frequency-division multiplex signal to an optical signal, c h a r a c t e r i z e d i n that the transmitter (SEN) further comprises a predistortion unit (VOR) for generating a frequency-division multiplex signal with different subcarrier signal levels, and that the predistortion unit (VOR) and the directly modulated laser (LAS) are connected in series.
2. A transmitter as claimed in claim 1, characterized in that an electric amplifier (AMP2) is connected between the predistortion unit (VOR) and the laser (LAS).
3. A transmitter (SEN) as claimed in claim 1, characterized in that the circuit of the predistortion unit (VOR) comprises a coil (L) in the series arm.
4. A transmitter (SEN) as claimed in claim 1, characterized in that the circuit of the predistortion unit (VOR) comprises a capacitor (C) in the shunt arm.
5. A transmitter (SEN) as claimed in claim 1, characterized in that in the predistortion unit (VOR), a frequency-division multiplex signal with subcarrier signal levels decaying for increasing frequencies is generable.
6. A transmitter (SEN) as claimed in claim 5, characterized in that the characteristic of the decaying subcarrier signal levels is inversely proportional to the characteristic of the expected distortions of the subcarrier signal levels on a given optical transmission line.
7. A method of optically transmitting an electric frequency-division multiplex signal consisting of multiplexed subcarrier signals with equal signal levels wherein the frequency-division multiplex signal is converted to an optical signal by means of a directly modulated laser (LAS), c h a r a c t e r i z e d i n that, before being converted to an optical signal, the frequency-division multiplex signal is converted in a predistortion unit (VOR) to a frequency-division multiplex signal with different subcarrier signal levels.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE1996135990 DE19635990A1 (en) | 1996-09-05 | 1996-09-05 | Transmitting device and method for the optical transmission of electrical frequency division multiplex signals |
| DE19635990.2 | 1996-09-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2213866A1 true CA2213866A1 (en) | 1998-03-05 |
Family
ID=7804675
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2213866 Abandoned CA2213866A1 (en) | 1996-09-05 | 1997-09-04 | Transmitter and method for optically transmitting electric frequency-division multiplex signals |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0828358A3 (en) |
| CA (1) | CA2213866A1 (en) |
| DE (1) | DE19635990A1 (en) |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2922952C2 (en) * | 1979-06-06 | 1982-10-21 | Siemens Ag, 1000 Berlin Und 8000 Muenchen | Arrangement for controlling the light emission of a light emitting diode |
| US5016242A (en) * | 1988-11-01 | 1991-05-14 | Gte Laboratories Incorporated | Microwave subcarrier generation for fiber optic systems |
| DE3907497A1 (en) * | 1989-03-08 | 1990-09-13 | Standard Elektrik Lorenz Ag | OPTICAL MESSAGE TRANSMISSION SYSTEM FOR THE SUBSCRIBER AREA |
| DE4121569A1 (en) * | 1991-06-29 | 1993-01-14 | Standard Elektrik Lorenz Ag | EQUALIZER FOR OPTICALLY TRANSMITTED MESSAGE SIGNALS |
-
1996
- 1996-09-05 DE DE1996135990 patent/DE19635990A1/en not_active Withdrawn
-
1997
- 1997-09-04 CA CA 2213866 patent/CA2213866A1/en not_active Abandoned
- 1997-09-04 EP EP97440075A patent/EP0828358A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| DE19635990A1 (en) | 1998-03-12 |
| EP0828358A2 (en) | 1998-03-11 |
| EP0828358A3 (en) | 2002-01-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |