CA2302097A1 - Optical amplifier with loop mirror filter noise reducer, and loop mirror filter per se - Google Patents
Optical amplifier with loop mirror filter noise reducer, and loop mirror filter per se Download PDFInfo
- Publication number
- CA2302097A1 CA2302097A1 CA 2302097 CA2302097A CA2302097A1 CA 2302097 A1 CA2302097 A1 CA 2302097A1 CA 2302097 CA2302097 CA 2302097 CA 2302097 A CA2302097 A CA 2302097A CA 2302097 A1 CA2302097 A1 CA 2302097A1
- Authority
- CA
- Canada
- Prior art keywords
- signal
- loop mirror
- coupler
- loop
- mirror filter
- 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
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06754—Fibre amplifiers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/08—Construction or shape of optical resonators or components thereof
- H01S3/081—Construction or shape of optical resonators or components thereof comprising three or more reflectors
- H01S3/083—Ring lasers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre
- H01S3/094011—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre with bidirectional pumping, i.e. with injection of the pump light from both two ends of the fibre
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
- H01S3/2308—Amplifier arrangements, e.g. MOPA
- H01S3/2325—Multi-pass amplifiers, e.g. regenerative amplifiers
- H01S3/235—Regenerative amplifiers
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Optics & Photonics (AREA)
- Lasers (AREA)
Abstract
In order to reduce amplified spontaneous emission noise in the output signal of an amplifier of the kind in which amplification introduces amplified spontaneous emission, for example an erbium-doped fiber amplifier, the amplified signal is filtered using a loop mirror filter. The loop mirror filter may comprise a 3-dB fiber coupler with a loop of regular single-mode fiber connected between two of its ports. The amplified signal and the filtered signal will be applied to, and extracted from, one of its other ports, conveniently by way of a circulator.
Description
OPTICAL AMPLIFIER WITH LOOP MIRROR FILTER NOISE REDUCER AND
LOOP MIRROR FILTER PER SE
DESCRIPTION
TECHNICAL FIELD:
This invention relates to optical amplifiers of the kind which employ spontaneous emission, such as, for example, erbium-doped fiber amplifiers.
BACKGROUND ART:
Optical amplifiers are used in various components of optical telecommunications systems, such as the usual transmitter and receiver, and as repeaters or in-line amplifiers. Such optical amplifiers typically use an optical fiber doped with a rare earth element, for example erbium, to provide stimulated emission which is used to amplify the signal. Unfortunately, spontaneous emission occurs, is amplified along with the input signal, and appears as noise in the output signal, reducing the signal-to-noise ratio. It is desirable to improve signal-to-noise ratio by removing or substantially reducing such ASE noise.
In an article entitled "In-band Amplified Spontaneous Emission Noise Filtering with a Dispersion-imbalanced Nonlinear Loop Mirror", OFC 1999, William S. Wong et al. disclosed an experimental set up which reduced noise by means of a non-linear optical loop mirror, i.e. formed by two fibers of different types, and with different lengths. The set up comprised an EDFA and an external ASE generator which injected the input signal and noise, respectively, via a 3-dB coupler and a circulator, into a dispersion-imbalanced loop mirror formed by another 50/50 coupler, two lengths of "Lucent TrueWave" optical fiber having different anomalous dispersion characteristics, and a polarization controller. The polarization controller was used to null loop transmissions at low power so as to minimize the effects of natural birefringence. The signal from the loop mirror was ported to a lightwave receiver which performed bit error rate measurements. A disadvantage of Wong et al.'s design is that the loop mirror is formed by a transmission line, which is about 24 km long. While this might be acceptable in an experimental set-up, it is not practical or useful in a real system. Also, Wong et al. must use high power levels to exploit the non-linearity of the fiber used in the loop in order to achieve transmission of the signal.
Japanese patent application No. 11087822A, published March 30, 1999, owned by Samsung Electron Co. Ltd., and naming Wang Hwang Seong-Taek as inventor, disclosed an arrangement for providing a high small-signal gain in an erbium-doped fibre amplifier. Seong-taek disclosed an EDFA
comprising a circulator, a wavelength selective coupler, a laser diode pump and an erbium-doped fiber connected to a loop mirror by a coupler. The amplified signal from the EDF is reflected by the loop mirror so that it passes through the EDF again, but in the opposite direction. A disadvantage of this arrangement is that, although gain might be increased, overall signal-to-noise ratio will deteriorate because the signal will pass through the amplifier twice, incurring spontaneous emission noise penalties each time. Although the loop mirror will remove about one half of the ASE resulting from the first pass through the EDF, the ASE resulting from the return pass will not be removed.
The present invention seeks to eliminate or at least mitigate these disadvantages of known systems.
DISCLOSURE OF INVENTION:
According to one aspect of the present invention, an optical amplifier comprises an amplifier section for amplifying an input signal by means producing spontaneous emission amplified signal and a loop mirror filter for filtering the amplified signal to remove amplified spontaneous emission.
Preferably, the loop mirror filter comprises a circulator, a 3-dB coupler and a loop of optical fiber, the circulator directing the amplified signal and the filtered signal to and from the loop of fiber. Preferably, the loop of optical fiber is relatively short, say less than 5 meters.
According to a second aspect of the invention there is provided a loop mirror filter for filtering amplified spontaneous emission produced by optical amplification, comprising a circulator, a 3-dB coupler and a loop of optical fiber, the circulator directing the amplified signal and the filtered signal to and from the loop of fiber.
LOOP MIRROR FILTER PER SE
DESCRIPTION
TECHNICAL FIELD:
This invention relates to optical amplifiers of the kind which employ spontaneous emission, such as, for example, erbium-doped fiber amplifiers.
BACKGROUND ART:
Optical amplifiers are used in various components of optical telecommunications systems, such as the usual transmitter and receiver, and as repeaters or in-line amplifiers. Such optical amplifiers typically use an optical fiber doped with a rare earth element, for example erbium, to provide stimulated emission which is used to amplify the signal. Unfortunately, spontaneous emission occurs, is amplified along with the input signal, and appears as noise in the output signal, reducing the signal-to-noise ratio. It is desirable to improve signal-to-noise ratio by removing or substantially reducing such ASE noise.
In an article entitled "In-band Amplified Spontaneous Emission Noise Filtering with a Dispersion-imbalanced Nonlinear Loop Mirror", OFC 1999, William S. Wong et al. disclosed an experimental set up which reduced noise by means of a non-linear optical loop mirror, i.e. formed by two fibers of different types, and with different lengths. The set up comprised an EDFA and an external ASE generator which injected the input signal and noise, respectively, via a 3-dB coupler and a circulator, into a dispersion-imbalanced loop mirror formed by another 50/50 coupler, two lengths of "Lucent TrueWave" optical fiber having different anomalous dispersion characteristics, and a polarization controller. The polarization controller was used to null loop transmissions at low power so as to minimize the effects of natural birefringence. The signal from the loop mirror was ported to a lightwave receiver which performed bit error rate measurements. A disadvantage of Wong et al.'s design is that the loop mirror is formed by a transmission line, which is about 24 km long. While this might be acceptable in an experimental set-up, it is not practical or useful in a real system. Also, Wong et al. must use high power levels to exploit the non-linearity of the fiber used in the loop in order to achieve transmission of the signal.
Japanese patent application No. 11087822A, published March 30, 1999, owned by Samsung Electron Co. Ltd., and naming Wang Hwang Seong-Taek as inventor, disclosed an arrangement for providing a high small-signal gain in an erbium-doped fibre amplifier. Seong-taek disclosed an EDFA
comprising a circulator, a wavelength selective coupler, a laser diode pump and an erbium-doped fiber connected to a loop mirror by a coupler. The amplified signal from the EDF is reflected by the loop mirror so that it passes through the EDF again, but in the opposite direction. A disadvantage of this arrangement is that, although gain might be increased, overall signal-to-noise ratio will deteriorate because the signal will pass through the amplifier twice, incurring spontaneous emission noise penalties each time. Although the loop mirror will remove about one half of the ASE resulting from the first pass through the EDF, the ASE resulting from the return pass will not be removed.
The present invention seeks to eliminate or at least mitigate these disadvantages of known systems.
DISCLOSURE OF INVENTION:
According to one aspect of the present invention, an optical amplifier comprises an amplifier section for amplifying an input signal by means producing spontaneous emission amplified signal and a loop mirror filter for filtering the amplified signal to remove amplified spontaneous emission.
Preferably, the loop mirror filter comprises a circulator, a 3-dB coupler and a loop of optical fiber, the circulator directing the amplified signal and the filtered signal to and from the loop of fiber. Preferably, the loop of optical fiber is relatively short, say less than 5 meters.
According to a second aspect of the invention there is provided a loop mirror filter for filtering amplified spontaneous emission produced by optical amplification, comprising a circulator, a 3-dB coupler and a loop of optical fiber, the circulator directing the amplified signal and the filtered signal to and from the loop of fiber.
BRIEF DESCRIPTION OF THE DRAWINGS:
Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which:
Figure 1 illustrates an optical telecommunications system comprising a transmitter, a repeater and a receiver, each of which includes an optical amplifier comprising an EDFA stage and a loop mirror filter;
Figure 2 illustrates one of the optical amplifiers in more detail.
BEST MODES FOR CARRYING OUT THE INVENTION:
Referring first to Figure 1, an optical telecommunications system comprises a transmitter section 10 comprising a light source 12, conveniently a laser source producing continuous wave (CW) light, a modulator 14, conveniently a lithium niobate device, and an optical power amplifier 16. The modulator 14 is connected between the light source 12 and the input of power amplifier 16 and modulates the CW light with the data to be transmitted. The output of the power amplifier 16 is connected by an optical fiber transmission line 18 to an in-line (repeater) amplifier 20, which is connected in turn by a second optical fiber transmission line 22 to a preamplifier 24, the output of which is connected to a receiver section 26 for extraction of the data in known manner.
The power amplifier 16, in-line amplifier 20 and preamplifier 24 comprise erbium-doped fiber amplifier stages (EDFAs) 28, 30 and 32, respectively, and loop mirror filters (LMFs) 34, 36 and 38, respectively. The LMFs 34, 36 and 38 remove amplified spontaneous emission (ASE) generated within the EDFAs 28, 30 and 32, respectively. It will be appreciated that the in-line amplifier is optional, the need for it depending upon the distance between the transmitter and the receiver.
The signal level at the input of the power amplifier 16 will be quite high, whereas the signal at the input of the preamplifier 24 and, possibly, that at the input of the in-line amplifier 20, will be relatively small. Consequently, the characteristics of the three EDFAs 28, 30 and 32 may be different. The LMFs 34, 36 and 38, however, may be identical. Since the three amplifiers are substantially identical, only the power amplifier 16 will now be described with reference to Figure 2, which shows the EDFA 28 and the LMF 34 in more detail.
As shown in Figure 2, the EDFA 28 comprises a first wavelength selective coupler 40, for combining the input signal with energy from a pump source 42 and applying it to one end of an erbium-doped fiber (EDF) 44.
Within the EDF 44, pump energy is transferred to the input signal causing amplification in known manner. The other end of the EDF 44 is connected to a wavelength demultiplexer 46 which extracts residual pump energy and supplies the amplified signal to input port P,N of the LMF 34. It should be appreciated that other kinds of EDFA could be employed, such as those disclosed in the present applicant's patent application No. (Attorney docket No.
AP690) filed contemporaneously herewith.
The LMF 34 comprises a circulator 48, a 3-dB coupler 50 having four ports identified as A, B, C and D, and a loop of optical fiber 52 connected between ports C and D of the coupler 50. The other two ports A and B of the coupler 50 are connected to a bidirectional port G of the circulator 48 and a first output port P1o~T of the LMF 34, respectively. The circulator 48 has a unidirectional input port F and a unidirectional output port E connected to the input port P,N and a second output port Pour, respectively.
The optical fiber 52 may comprise single mode fiber, such as that marketed as type SMF-28 by Corning Inc., and preferably is as short as possible to avoid polarization fluctuations. Typically, its length will be of the order of 5 meters.
In operation, the signal leaving the circulator 48 and entering port A of the coupler 50 is a coherent signal and has a certain phase. The coupler 50 splits the signal equally into 50 per cent signals CW and CCW which leave the coupler 50 via its output ports C and D, respectively, so that they propagate in opposite directions around the loop of single-mode fiber 52. The signal CW
propagating clockwise (as shown) in the loop 52 will be in phase with the signal at port A. The signal CCW leaving port D and propagating counterclockwise will be phase-shifted through rr/2 radians relative to the clockwise signal CW. When the signals CW and CCW arrive back at the opposite ports D and C, respectively, and pass through the fibre coupler 50, again, the reflected signal appearing at port A will be sum of the clockwise signal CW and the counterclockwise signal CCW, and be phase-shifted relative to the input signal by n/2 radians. In theory, there should be no output signal from output port P1 our because the whole energy should be reflected in the 5 loop mirror formed by fibre 52 and the coupler 50. In practice, there will be some slight leakage because the coupler 50 will not split at exactly 50 per cent.
The ASE noise that is generated by the EDFA 28, however, is not coherent, but is random noise. Consequently, on average about one half of the ASE noise will appear at port B of the coupler 50, and hence at output port P1 our, and only the remainder of the ASE noise will appear at port A along with the reflected signal. Hence, the loop mirror will reduce the ASE noise appearing in the output signal at port P2our by, on average, about 50 per cent.
It is envisaged that an improvement in overall noise figure could be achieved by using polarization maintaining components including polarization maintaining fiber. Additionally or alternatively, a polarization controller could be added, conveniently between the circulator 48 and the 3-dB coupler 50. If a polarization controller is used, the EDFA need not use polarization maintaining components or be constrained to provide a particular state of polarization.
It has been demonstrated that the performance of the optical amplifier 12 can be enhanced, especially for low input signal power, by inserting an isolator between the output of EDFA 28 and the input of LMF 34 to avoid or reduce Rayleigh backscattering.
It is further envisaged that a polarization controller could be inserted into the loop mirror to direct the filtered amplified signal to the fourth port B
of the 3-dB coupler 50, and the circulator 48 replaced by an isolator. A second isolator might then be inserted between the coupler 50 and the output port P1 our It should be appreciated that the above-described noise reduction technique using a loop mirror filter is not limited to use with erbium-doped fibre amplifiers, but is applicable to any device which produces amplified spontaneous emission and can benefit by its removal so as to improve the ~_.____ s . __ __ signal to noise ratio. Accordingly, the invention encompasses a loop mirror filter per se.
INDUSTRIAL APPLICABILITY
An advantage of optical amplifiers according to the present invention, at least as compared with that disclosed by Wong et al, is that they use a loop mirror fiber that typically is less than 5 m, and may be an ordinary single mode filter. A polarization controller is not essential, since satisfactory noise reduction can be achieved based solely upon destructive interference in the coupler.
Because optical amplifiers according to the present invention pass the signal through the EDF once only, they should yield better signal-to-noise ratios than, for example, that disclosed in the afore-mentioned Japanese patent application No. 11087822A.
Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings in which:
Figure 1 illustrates an optical telecommunications system comprising a transmitter, a repeater and a receiver, each of which includes an optical amplifier comprising an EDFA stage and a loop mirror filter;
Figure 2 illustrates one of the optical amplifiers in more detail.
BEST MODES FOR CARRYING OUT THE INVENTION:
Referring first to Figure 1, an optical telecommunications system comprises a transmitter section 10 comprising a light source 12, conveniently a laser source producing continuous wave (CW) light, a modulator 14, conveniently a lithium niobate device, and an optical power amplifier 16. The modulator 14 is connected between the light source 12 and the input of power amplifier 16 and modulates the CW light with the data to be transmitted. The output of the power amplifier 16 is connected by an optical fiber transmission line 18 to an in-line (repeater) amplifier 20, which is connected in turn by a second optical fiber transmission line 22 to a preamplifier 24, the output of which is connected to a receiver section 26 for extraction of the data in known manner.
The power amplifier 16, in-line amplifier 20 and preamplifier 24 comprise erbium-doped fiber amplifier stages (EDFAs) 28, 30 and 32, respectively, and loop mirror filters (LMFs) 34, 36 and 38, respectively. The LMFs 34, 36 and 38 remove amplified spontaneous emission (ASE) generated within the EDFAs 28, 30 and 32, respectively. It will be appreciated that the in-line amplifier is optional, the need for it depending upon the distance between the transmitter and the receiver.
The signal level at the input of the power amplifier 16 will be quite high, whereas the signal at the input of the preamplifier 24 and, possibly, that at the input of the in-line amplifier 20, will be relatively small. Consequently, the characteristics of the three EDFAs 28, 30 and 32 may be different. The LMFs 34, 36 and 38, however, may be identical. Since the three amplifiers are substantially identical, only the power amplifier 16 will now be described with reference to Figure 2, which shows the EDFA 28 and the LMF 34 in more detail.
As shown in Figure 2, the EDFA 28 comprises a first wavelength selective coupler 40, for combining the input signal with energy from a pump source 42 and applying it to one end of an erbium-doped fiber (EDF) 44.
Within the EDF 44, pump energy is transferred to the input signal causing amplification in known manner. The other end of the EDF 44 is connected to a wavelength demultiplexer 46 which extracts residual pump energy and supplies the amplified signal to input port P,N of the LMF 34. It should be appreciated that other kinds of EDFA could be employed, such as those disclosed in the present applicant's patent application No. (Attorney docket No.
AP690) filed contemporaneously herewith.
The LMF 34 comprises a circulator 48, a 3-dB coupler 50 having four ports identified as A, B, C and D, and a loop of optical fiber 52 connected between ports C and D of the coupler 50. The other two ports A and B of the coupler 50 are connected to a bidirectional port G of the circulator 48 and a first output port P1o~T of the LMF 34, respectively. The circulator 48 has a unidirectional input port F and a unidirectional output port E connected to the input port P,N and a second output port Pour, respectively.
The optical fiber 52 may comprise single mode fiber, such as that marketed as type SMF-28 by Corning Inc., and preferably is as short as possible to avoid polarization fluctuations. Typically, its length will be of the order of 5 meters.
In operation, the signal leaving the circulator 48 and entering port A of the coupler 50 is a coherent signal and has a certain phase. The coupler 50 splits the signal equally into 50 per cent signals CW and CCW which leave the coupler 50 via its output ports C and D, respectively, so that they propagate in opposite directions around the loop of single-mode fiber 52. The signal CW
propagating clockwise (as shown) in the loop 52 will be in phase with the signal at port A. The signal CCW leaving port D and propagating counterclockwise will be phase-shifted through rr/2 radians relative to the clockwise signal CW. When the signals CW and CCW arrive back at the opposite ports D and C, respectively, and pass through the fibre coupler 50, again, the reflected signal appearing at port A will be sum of the clockwise signal CW and the counterclockwise signal CCW, and be phase-shifted relative to the input signal by n/2 radians. In theory, there should be no output signal from output port P1 our because the whole energy should be reflected in the 5 loop mirror formed by fibre 52 and the coupler 50. In practice, there will be some slight leakage because the coupler 50 will not split at exactly 50 per cent.
The ASE noise that is generated by the EDFA 28, however, is not coherent, but is random noise. Consequently, on average about one half of the ASE noise will appear at port B of the coupler 50, and hence at output port P1 our, and only the remainder of the ASE noise will appear at port A along with the reflected signal. Hence, the loop mirror will reduce the ASE noise appearing in the output signal at port P2our by, on average, about 50 per cent.
It is envisaged that an improvement in overall noise figure could be achieved by using polarization maintaining components including polarization maintaining fiber. Additionally or alternatively, a polarization controller could be added, conveniently between the circulator 48 and the 3-dB coupler 50. If a polarization controller is used, the EDFA need not use polarization maintaining components or be constrained to provide a particular state of polarization.
It has been demonstrated that the performance of the optical amplifier 12 can be enhanced, especially for low input signal power, by inserting an isolator between the output of EDFA 28 and the input of LMF 34 to avoid or reduce Rayleigh backscattering.
It is further envisaged that a polarization controller could be inserted into the loop mirror to direct the filtered amplified signal to the fourth port B
of the 3-dB coupler 50, and the circulator 48 replaced by an isolator. A second isolator might then be inserted between the coupler 50 and the output port P1 our It should be appreciated that the above-described noise reduction technique using a loop mirror filter is not limited to use with erbium-doped fibre amplifiers, but is applicable to any device which produces amplified spontaneous emission and can benefit by its removal so as to improve the ~_.____ s . __ __ signal to noise ratio. Accordingly, the invention encompasses a loop mirror filter per se.
INDUSTRIAL APPLICABILITY
An advantage of optical amplifiers according to the present invention, at least as compared with that disclosed by Wong et al, is that they use a loop mirror fiber that typically is less than 5 m, and may be an ordinary single mode filter. A polarization controller is not essential, since satisfactory noise reduction can be achieved based solely upon destructive interference in the coupler.
Because optical amplifiers according to the present invention pass the signal through the EDF once only, they should yield better signal-to-noise ratios than, for example, that disclosed in the afore-mentioned Japanese patent application No. 11087822A.
Claims (4)
1. An optical amplification device comprising an amplifier stage for amplifying an input signal by means producing amplified spontaneous emission to produce an amplified signal and a loop mirror filter for filtering the amplified signal to remove said amplified spontaneous emission.
2. An optical amplification device comprising an input port for reception of an input signal for amplification and an output port, an active fiber coupled to the input port to receive the input signal, pump means for supplying pump energy to the active fiber, means for extracting the amplified signal from the active fiber, and a loop mirror filter for filtering the amplified signal to remove amplified spontaneous emission noise and supplying the filtered signal to the output port.
3. An optical amplifier according to claim 1 or 2, wherein the loop mirror filter comprises a 3-dB coupler and a loop of optical fiber with its respective ends connected to two ports of the coupler, the coupler having a third port for receiving the amplified signal.
4. An optical filter for filtering an input signal to remove noise comprising a loop mirror formed by a 3-dB coupler and a loop of optical fiber with its ends connected to two ports, respectively, of the coupler, the coupler having a third port for receiving the input signal.
Priority Applications (7)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2302097 CA2302097A1 (en) | 2000-03-24 | 2000-03-24 | Optical amplifier with loop mirror filter noise reducer, and loop mirror filter per se |
| US09/805,937 US6404541B2 (en) | 2000-03-24 | 2001-03-15 | Optical amplifier with active-fiber loop mirror |
| CA002341816A CA2341816A1 (en) | 2000-03-24 | 2001-03-21 | Optical amplifier with active-fiber loop mirror |
| CA 2341824 CA2341824A1 (en) | 2000-03-24 | 2001-03-21 | Optical amplifier with loop mirror filter noise reducer, and loop mirror filter per se |
| US09/813,854 US6490380B2 (en) | 2000-03-24 | 2001-03-22 | Optical amplifier with loop mirror filter noise reducer, and loop mirror filter per se |
| CN 01119023 CN1316671A (en) | 2000-03-24 | 2001-03-23 | Light amplifier with active optical fibre ring reflector |
| EP20010302740 EP1139519A2 (en) | 2000-03-24 | 2001-03-23 | Optical amplifier with active-loop mirror |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2302097 CA2302097A1 (en) | 2000-03-24 | 2000-03-24 | Optical amplifier with loop mirror filter noise reducer, and loop mirror filter per se |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2302097A1 true CA2302097A1 (en) | 2001-09-24 |
Family
ID=4165632
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2302097 Abandoned CA2302097A1 (en) | 2000-03-24 | 2000-03-24 | Optical amplifier with loop mirror filter noise reducer, and loop mirror filter per se |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2302097A1 (en) |
-
2000
- 2000-03-24 CA CA 2302097 patent/CA2302097A1/en not_active Abandoned
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5815308A (en) | Bidirectional optical amplifier | |
| EP0789432B1 (en) | Low noise optical fiber raman amplifier and communication system comprising such an amplifier | |
| KR100265788B1 (en) | Optical fiber amplifier having high small signal gain | |
| CA2267775C (en) | A multi-wavelength optical pump | |
| US5481391A (en) | Optical fiber system and method for overcoming the effects of polarization gain anisotropy in a fiber amplifier | |
| JPH08204636A (en) | Optical communication system | |
| EP0660468B1 (en) | Bidirectional optical amplifier | |
| US8081880B2 (en) | Inline pump sharing architecture for remotely-pumped pre- and post-amplifiers | |
| US6934078B2 (en) | Dispersion-compensated erbium-doped fiber amplifier | |
| US6404541B2 (en) | Optical amplifier with active-fiber loop mirror | |
| US6862132B1 (en) | Suppression of double rayleigh backscattering and pump reuse in a raman amplifier | |
| NZ243246A (en) | Fibre optic amplifier with optical isolator to reduce noise | |
| US6490380B2 (en) | Optical amplifier with loop mirror filter noise reducer, and loop mirror filter per se | |
| JPH03135081A (en) | Optical amplifier | |
| CA2302097A1 (en) | Optical amplifier with loop mirror filter noise reducer, and loop mirror filter per se | |
| JP2008053756A (en) | Optical fiber amplifier | |
| EP1139519A2 (en) | Optical amplifier with active-loop mirror | |
| JP2002217477A (en) | Optical amplifier | |
| CA2341824A1 (en) | Optical amplifier with loop mirror filter noise reducer, and loop mirror filter per se | |
| JP2801359B2 (en) | Erbium-doped fiber optical amplifier | |
| CA2615306C (en) | Inline pump sharing architecture for remotely-pumped pre-and post-amplifiers | |
| KR100603595B1 (en) | Bidirectional two-stage optical amplifier | |
| KR20030075295A (en) | An Gain clamped erbium-doped fiber amplifier for long wavelength band | |
| US20020122243A1 (en) | Distributed gain optical fiber amplifier | |
| JP2001028569A (en) | Hybrid raman amplifier |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |