Optical amplifier for amplifying polarised signal light
Patent Information
- Application Number
- EP2023725955
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-04-21
- Filing Date
- 2023-04-19
- Publication Date
- 2025-02-26
AI Technical Summary
Existing optical amplifiers for polarized signal light suffer from frequency fluctuations due to changes in the optical path length of the optical fiber, leading to uncertainty in signal transmission, as they typically have different polarizations for signal and rear light, causing errors in compensating for environmental influences.
An optical amplifier with a taillight polarization adjuster that matches the polarization of the rear light to the signal light, and optionally a signal light polarization divider to adjust the signal light polarization to a predetermined target polarization, ensuring both lights have the same polarization, thereby reducing frequency uncertainty.
This configuration allows for the transmission of signal light with lower uncertainty by eliminating errors caused by polarization-dependent optical path length fluctuations, achieving stable frequency transmission over long distances.
Smart Images
Figure 1.1
Abstract
Description
[0001] Optical amplifier for amplifying polarized signal light
[0002] The invention relates to an optical amplifier for amplifying polarized signal light, comprising (a) an optical fiber for guiding the signal light, which has (i) a signal light input for coupling in the signal light and (ii) a signal light output which is spaced from the signal light input, (b) a signal light Brillouin amplifier which has (i) a signal light amplification pump laser which is designed to generate signal light amplification pump light, which (ii) is arranged to amplify the signal light by means of stimulated Brillouin scattering and (iii) a signal light amplification pump light coupler for coupling the signal light amplification pump light into the optical fiber.
[0003] Such optical amplifiers are used to provide a frequency from a frequency source to a natural frequency receiver located at a location remote from the frequency source. An optical fiber is arranged between the frequency source and the frequency receiver to guide the signal light. Changes in the environment of the optical fiber cause fluctuations in the optical path length of the optical fiber. These fluctuations lead to a fluctuation in the frequency of the signal light at the frequency receiver. To reduce the uncertainty with which the frequency is received at the frequency receiver, these frequency fluctuations must be compensated.
[0004] This often occurs because the signal light is reflected at the frequency receiver. The resulting backlight travels through the same optical fiber, so the effect of the changing optical path length is reflected twice in the backlight. In this way, the interference caused by the changing optical path length can be determined and compensated. Furthermore, the intensity of the signal light decreases in the optical fiber. If the frequency is to be transmitted over longer distances, the signal light and the backlight must be amplified. It is desirable to minimize the uncertainty in the frequency transmission.
[0005] The invention is based on the object of improving the amplification of signal light, in particular for transmitting a frequency from a frequency source to a frequency receiver.
[0006] The invention solves the problem by a generic optical amplifier with a taillight polarization controller, which is designed to adjust a taillight polarization of taillight incident through the signal light output, so that the taillight polarization corresponds to a signal light polarization of the signal light.
[0007] Alternatively or additionally, the optical amplifier has a signal light polarization adjuster which is designed to adjust a signal light polarization of the signal light incident through the signal light output to a predetermined signal light target polarization, in particular so that the signal light polarization corresponds to the rear light polarization of the rear light.
[0008] An advantage of the invention is that the frequency of the signal light can be transmitted with particularly low uncertainty. State-of-the-art amplifiers are designed such that the reverse light polarization differs from the signal light polarization. For example, the two polarizations are perpendicular to each other. This, however, results in the frequency correction being performed based on frequency fluctuations experienced by light of different polarization directions. However, it has been found that environmental influences acting on the optical fiber lead to fluctuations in the optical path length that are dependent on the polarization. Therefore, an error can occur when compensating for fluctuations in the optical path lengths of the optical fiber. Because the signal light and the reverse light have the same polarization in the optical amplifier according to the invention, this error cannot occur.The frequency can therefore be transmitted with less uncertainty. For the purposes of this description, the signal light input refers to a component or location of the optical amplifier into which signal light can be coupled.
[0009] The signal light output is a component or location of the optical amplifier where the signal light is coupled out or exits the optical amplifier. Typically, the optical amplifier is a self-contained device, but it is also possible for the optical fiber used to transmit the signal light and the tail light to extend to the frequency source and / or frequency receiver.
[0010] The signal light Brillouin amplifier is an amplifier that amplifies light based on stimulated Brillouin scattering.
[0011] An optical fiber is a fiber designed to conduct signal light. The optical fiber is preferably a glass fiber.
[0012] The feature that the rear light polarization corresponds to the signal light polarization is understood in particular to mean that the polarization plane of the rear light at the signal light polarization controller corresponds to the polarization plane of the signal light at the signal light polarization controller and / or that the polarization plane of the rear light at the rear light polarization controller corresponds to the polarization plane of the signal light at the rear light polarization controller. It is possible, but not necessary, for the polarization planes to be identical, i.e., the angle between the two polarization planes is zero. However, it is also possible for the angle to be no more than 10°, in particular no more than 5°.
[0013] According to a preferred embodiment, the optical amplifier has a signal light polarization meter for determining the signal light polarization Ps. The signal light polarization can be determined using this signal light polarization meter. The taillight polarization controller is coordinated with the signal light polarization meter so that the taillight polarization controller can adapt the polarization of the taillight to that of the signal light. It should be noted that it is irrelevant to the optical amplifier which light is considered a signal light and which light is considered a taillight. Light from a frequency source can also be considered a taillight, and the light emitted by the frequency receiver can also be considered a signal light. The naming of the signals as signal light and taillight is merely for ease of description.
[0014] It is particularly advantageous if the optical amplifier has a signal light polarization adjuster designed to adjust the signal light polarization to a predetermined signal light target polarization Ps.soii. In this case, the signal light polarization meter is a component of the signal light polarization adjuster. The signal light target polarization corresponds in particular to the polarization at which the maximum amplification occurs in the optical amplifier. In particular, the signal light target polarization is selected such that, at a beam splitter for coupling the signal light amplification pump light, the signal light amplification pump light has the same polarization as the signal light.It is particularly advantageous if the signal light polarization meter is designed in such a way that the polarization of the signal light amplification pump light can also be determined, and for the polarization adjustment of signal light and signal light amplification pump light.
[0015] According to a preferred embodiment, the optical amplifier has a backlight Brillouin amplifier which comprises (a) a backlight amplification pump laser configured to generate backlight amplification pump light, and (b) is arranged to amplify the backlight by means of stimulated Brillouin scattering and (c) a signal light amplification pump light coupler for coupling the signal light amplification pump light into the optical fiber.
[0016] In this way, the optical amplifier is a bidirectional amplifier that amplifies both the signal light and the tail light. It is advantageous if the tail light amplification pump laser and the signal light amplification pump laser are arranged in a common housing or two connected housings.
[0017] The advantage of this optical amplifier is that it is versatile. It can be advantageous to distribute the optical frequency from the frequency source not just to one frequency receiver, but to two, three, or more frequency receivers. In this case, in order to determine the change in the optical path length, it is necessary to know which frequency receiver the rear light was reflected from. This can be achieved, for example, by each frequency receiver modulating an additional constant offset frequency onto the rear light. To achieve the best possible amplification, however, the Brillouin frequency must be precisely matched. An offset frequency must therefore be compensated in the amplifier. By using two pump lasers, the amplifier can be easily adapted to different offset frequencies.
[0018] According to a preferred embodiment, the optical amplifier has (a) a backlight pump light frequency modulator for changing a backlight pump light frequency (VB) of the backlight amplification pump light, (b) a backlight intensity meter for measuring a backlight intensity of the backlight, which is arranged in front of the backlight amplification pump light coupler in the backlight propagation direction, and (c) a backlight frequency control which is connected to the backlight amplification pump light frequency modulator and the backlight intensity meter for controlling the backlight pump light frequency (VB) to maximum backlight intensity.
[0019] The advantage of this is that particularly high amplification can be achieved. Maximum amplification occurs at the Brillouin frequency, but this frequency can fluctuate. The backlight frequency control ensures that the backlight amplification pump light always corresponds as closely as possible to the Brillouin frequency.
[0020] It is advantageous if the signal light Brillouin amplifier includes a Brillouin frequency detection device for time-dependent detection of a Brillouin frequency VBFS at which the signal light is maximally amplified, wherein the Brillouin frequency detection device is connected to the signal light amplification pump laser for adjusting the signal light pump frequency VF. In this way, the optimal amplification of the signal light is achieved, as described above for the amplification of the rear light.
[0021] Preferably, the Brillouin frequency detection device comprises (a) a signal light amplification pump light frequency modulator for changing a signal light pump light frequency VF of the signal light pump light, (b) a signal light intensity meter for measuring a signal light intensity of the signal light in the signal light propagation direction, which is arranged in front of the signal light amplification pump light coupler signal light input, and (c) a signal light frequency controller connected to the signal light amplification pump light frequency modulator and the signal light intensity meter for controlling the signal light pump light frequency to maximum signal light intensity.
[0022] Brillouin amplification is optimal when the pump light has the same polarization as the light to be amplified. Therefore, the optical amplifier preferably has a pump laser polarization adjustment device configured to control or regulate a backlight amplification pump light polarization of the backlight amplification pump light and / or a signal light amplification pump light polarization of the signal light amplification pump light, so that these polarizations correspond to one another in the optical fiber.
[0023] It is possible that the pump laser polarization adjustment device is connected only to the signal light pump laser, only to the backlight pump laser, or to both pump lasers and controls the respective polarization.
[0024] Preferably, the pump laser polarization adjustment device comprises (a) a low-frequency photodiode that determines a beat frequency (fb2) between the backlight pump frequency (VB) and the signal light pump frequency (VF), and (b) a phase-locked loop connected to the low-frequency photodiode and the signal light amplification pump laser and / or the backlight amplification pump laser. A low-frequency photodiode is understood to be a photodiode that can detect frequencies between 0 MHz and 500 MHz.
[0025] Preferably, the low-frequency photodiode is designed to detect a frequency between 50 and 250 MHz.
[0026] To adjust the signal light pump frequency VF, the signal light Brillouin amplifier preferably has a signal light phase stabilization device comprising a high-frequency photodiode. The high-frequency photodiode is preferably arranged to detect a beat frequency fbi between a signal light frequency vs of the signal light and the signal light pump frequency VF.
[0027] Preferably, the optical amplifier (a) has a beam splitter with a signal light input connected to the signal light input port, in particular the signal light polarization meter, a backlight input connected to the signal light output, in particular the backlight polarization controller, a signal light amplification pump light input connected to the signal light amplification pump laser, and a backlight amplification pump light input connected to the backlight amplification pump laser. It is advantageous if the optical amplifier (b) has a circulator, which is connected to the beam splitter with a first port, to the backlight amplification pump laser with a second port, and to the low-frequency photodiode with a third port.
[0028] Alternatively or additionally, the optical amplifier can comprise (a) a signal light amplification pump laser cavity comprising (i) a highly reflective signal light amplification pump light coupling element and (ii) an optical isolator, (iii) wherein the signal light impinges on the signal light amplification pump light coupling element at an angle of incidence to a normal, and (b) a return light amplification pump laser cavity comprising (i) a highly reflective return light amplification pump light coupling element and (ii) an optical isolator, (iii) wherein the return light impinges on the return light coupling element at an angle of incidence to a normal. The advantage of this arrangement is that it is both highly effective for the signal light and couples the signal light amplification pump light into the optical fiber with high efficiency.Preferably, the length of the signal light amplification pump laser cavity is configured such that the incoming backlight, which is frequency-shifted relative to the signal light amplification pump light, lies in the transmission minimum of the signal light amplification pump laser cavity. Preferably, the length of the backlight amplification pump laser cavity is configured such that the incoming signal light lies in the transmission minimum of the backlight amplification pump laser cavity.
[0029] According to the invention, there is also provided an optical network comprising (a) a frequency source for emitting signal light, (b) a frequency receiver, (c) an optical fiber line from the frequency source to the frequency receiver, (d) at least one optical amplifier according to one of the preceding claims, which (i) is arranged between the frequency source and the frequency receiver, (ii) has a signal light input for coupling in the signal light and (iii) has a signal light output spaced from the signal light input, (iv) has a signal light amplification pump laser configured to generate signal light amplification pump light, (v) is arranged to amplify the signal light by means of stimulated Brillouin scattering and (vi) has a signal light amplification pump light coupler for coupling the signal light amplification pump light into the optical fiber, (e) a backlight polarization controller,which is designed to set a rear light polarization of the rear light that corresponds to a signal light polarization of the signal light and / or a signal light polarization controller which is designed to set a signal light polarization of the signal light to a predetermined signal light target polarization.,
[0030] The distance between the frequency source and the frequency receiver is preferably at least 100 km. The frequency source is preferably an atomic clock. According to a preferred embodiment, this atomic clock has an Allan variance of at most 10 -16 , in particular no more than 10' 17 , with an averaging time T of 100 seconds.
[0031] The invention also provides a cascade of at least two optical amplifiers according to the preamble of claim 1, which have a signal light polarization controller. The signal light polarization controller of the next optical amplifier in the signal light propagation direction then compensates for the polarization fluctuations of the optical fiber line.
[0032] The invention is explained in more detail below with reference to the accompanying drawings.
[0033] Figure 1 shows the structure of an optical amplifier according to the invention,
[0034] Figure 2 in sub-figure 2a the dependence of the gain on the signal light pumping frequency VF and in sub-figure 2b additionally the dependence of the normalized phase shift on the signal light pumping frequency VF and
[0035] Figure 3 shows schematic arrangements of optical amplifiers according to further embodiments in Figures 3a and 3b. Figure 1 shows a circuit diagram of an optical amplifier 10 according to the invention for amplifying polarized signal light 12, which is schematically indicated by an arrow. The optical amplifier 10 has a polarization-maintaining optical fiber 14 for guiding the signal light from a signal light input 16 to a signal light output 18. Signal light 12 entering the signal light input 16 is amplified by a signal light Brillouin amplifier 20. The gain is preferably at least 30 dB.
[0036] The signal light Brillouin amplifier 20 has a signal light amplification pump laser 22 for generating signal light amplification pump light 24 with a signal light pump frequency VF and a signal light amplification pump laser polarization P24. The signal light amplification pump light 24 is fed into the optical fiber 14 by means of a beam splitter 26, counter to the propagation direction of the signal light 12. The beam splitter 26 can, for example, be a 35 / 65 beam splitter.
[0037] A taillight polarization controller 28 changes a taillight amplification pump laser polarization P28 of taillight 28 incident on the signal light output 18 so that it corresponds to the signal light amplification pump laser polarization P24. For this purpose, the taillight polarization controller 28 has a taillight polarization meter 32 for measuring the taillight polarization P28 and a polarization rotator 34 connected thereto. In the taillight propagation direction behind the taillight polarization controller 28, the taillight 30 has a desired taillight polarization Pao.soii. At the same time, the taillight polarization meter 32 measures the taillight amplification pump laser polarization for controlling or regulating the taillight amplification pump laser polarization.
[0038] A signal light polarization meter 36 is arranged downstream of the signal light input 16 in the direction of light propagation and detects a signal light polarization P12. The signal light polarization meter 36 is preferably part of a signal light polarization controller 38, which has a second polarization rotator 40 and rotates the signal light polarization P12 such that it corresponds to a desired signal light polarization Pi2,soii upon entering the beam splitter 26. In particular, the signal light polarization P12 is adapted to the signal light amplification pump laser polarization.
[0039] Preferably, Pi2,soii = P24. A portion of the signal light 12 is coupled out by means of a first coupler 42.1 and fed to a high-frequency photodiode 44, where it is superimposed with signal light amplification pump light 24. This creates a beat frequency fbi. A first optical phase-locked loop 46 controls the signal light amplification pump laser 22 such that the signal light amplification pump light 24 has a frequency that is higher than the signal light frequency vs by the Brillouin frequency VBFS. The Brillouin frequency is approximately VBFS = 11 GHz.
[0040] Signal light amplification pump light 24 is, in this case, guided through beam splitter 26 by means of a second coupler 42.2 to a low-frequency photodiode 50, where it is superimposed with backlight amplification pump light 52 from a backlight amplification pump laser 54. This creates a second oscillation frequency fb2, which corresponds to an offset frequency voffset between the signal light frequency vs and the frequency of the backlight. The offset frequency lies, for example, in the interval voffset e [50 MHz; 150 MHz].
[0041] By means of a second optical phase-locked loop 55, the rear light pump frequency VB of the rear light amplification pump light 52 is controlled to VB = vs +VBFS + voffset.
[0042] The backlight amplification pump light 52 is guided to the beam splitter 26 via a circular gate 48. For this purpose, a first port p1 of the circular gate 48 is connected to the beam splitter 26. A second port p2 is connected to the backlight amplification pump laser 54, and a third port p3 leads to the second coupler 42.2.
[0043] The two pump lasers 22 and 54, for example, are distributed feedback lasers. They can have a bandwidth of 2 MHz ±10% and an optical output power of, for example, 100 milliwatts.
[0044] The second optical phase-locked loop 55 can be implemented as an FPGA (field-programmable gated array). The bandwidth of the phase-locked loop 54 is, for example, 300 kHz.
[0045] The first phase-locked loop 46 is designed as a Brillouin frequency detection device and signal light frequency control, which interacts with a signal light amplification pump light frequency modulator 56 of the signal light amplification pump laser 22 and can change the signal light pump light frequency VF.
[0046] Figure 2a shows the variation of the signal light pump frequency VF as a function of time t. For example, the signal light pump frequency VF fluctuates in the interval [vF-v ar; vF+vvar] with a variation frequency v V ar. For the variation frequency, for example, Vvar —7.5 MHz applies.
[0047] The signal light intensity 112 of the amplified signal light is plotted below the time-dependently fluctuating signal light pump frequency VF, which is measured by a signal light intensity meter 58. The intensity of the tail light is measured by a tail light intensity meter 59.
[0048] Figure 2b shows the dependence of the signal light gain normalized to 1 on the difference between the rear light pump light frequency VF and the signal light frequency vs.
[0049] Figure 1 shows that the optical amplifier 10 may comprise a pump laser polarization adjustment device in the form of a signal light amplification polarization adjustment device 60, which is designed to control or regulate the signal light amplification pump laser polarization P24 so that it corresponds to a backlight amplification pump light polarization P52 of the backlight amplification pump light 52 in the optical fiber 14.
[0050] This signal light amplification polarization adjusting device 60 comprises a device for measuring and a device for changing the signal light amplification pump laser polarization P24.
[0051] Alternatively or additionally, the backlight amplification pump laser 54 may include a backlight amplification polarization adjusting device 62 for adjusting the backlight amplification pump light polarization Ps2 to the signal light amplification pump laser polarization P24.
[0052] Figure 3a shows a second embodiment of an optical amplifier 10 according to the invention, which has a signal light amplification pump laser cavity 64 and a return light amplification pump laser cavity 66. The signal light amplification pump laser cavity 64 has a first highly reflective signal light amplification pump light coupling element 68.1, which can be designed, for example, as a volume Bragg grating, and a first optical isolator 70.1. For example, the reflectance of the signal light amplification pump light 68.1 is at least 90%. The length of the signal light amplification pump laser cavity is preferably designed such that the coupling-in return light lies at a transmission minimum of the signal light amplification pump laser cavity or is filtered out by other properties.
[0053] The backlight laser cavity 66 has a highly reflective backlight amplification pump light coupling element 68.2 and a second optical isolator 70.2. Preferably, the length of the backlight amplification pump laser cavity is configured such that the coupling-in signal light lies at a transmission minimum of the signal light amplification pump laser cavity or is filtered out by other properties.
[0054] Figure 3b shows a third embodiment of an optical amplifier 10 according to the invention, which has an additional signal light amplification pump laser 74.1, which is phase-coupled to the signal light amplification pump light enhancement cavity 64. A further laser 74.2 is phase-coupled to the backlight amplification pump light enhancement cavity 66.
[0055] An optical network 76 according to the invention (see Figure 1) has a frequency source 78, in particular an atomic clock, and a frequency receiver 80. The optical fiber 82 leads from the frequency source 78 to the signal light input 16.
[0056] List of reference symbols
[0057] 10 optical amplifier 62 rear light amplification Polansa-
[0058] 12 Signal light adjustment device
[0059] 14 optical fiber 64 signal light laser cavity
[0060] 16 Signal light input 66 Tail light laser cavity
[0061] 18 Signal light output 68.1 Signal light coupling element
[0062] 20 Signal light Brillouin amplifier 68.2 Rear light coupling element
[0063] 22 Signal light amplification pump laser 70 optical isolator
[0064] 24 Signal light amplification pump light 72 Brillouin amplifier
[0065] 26 beam splitters 74 lasers
[0066] 28 Rear light polarization controller 76 Network
[0067] 30 Rear light 78 Frequency source
[0068] 32 rear light polarization meter 80 frequency receiver
[0069] 34 Rear light polarization rotator VB Rear light pump light frequency
[0070] 36 Signal light polarization meter VBFS Brillouin frequency
[0071] 38 Signal light polarization controller VF Signal light pump light frequency
[0072] 40 Signal light polarization rotator voffset offset frequency
[0073] 42 Coupler vs Signal Light Frequency
[0074] 44 high-frequency photodiode
[0075] 46 Phase locked loop fbi first beat frequency
[0076] 48 Circulator fb2 second beat frequency
[0077] 50 Low frequency photodiode I12 Signal light intensity
[0078] 52 Rear light boost pump light p port
[0079] 54 Rear light amplification pump laser P12 Signal light polarization
[0080] 55 second phase-locked loop, Pi2,soii signal light target polarization signal light frequency control
[0081] P24 Signal light amplification pump
[0082] 56 Signal light amplification laser polarization pump light frequency modulator
[0083] P30 rear light polarization
[0084] 58 Signal Light Intensity Meter
[0085] P30,soii rear light target polarization
[0086] 59 Rear light intensity meter
[0087] P52 taillight boost pump light
[0088] 60 Signal light amplification polarization polarization adjustment device t time
Claims
Patent claims 1. Optical amplifier for amplifying polarized signal light (12), with (a) an optical fiber (14) for guiding the signal light (12), which (i) a signal light input (16) for coupling in the signal light (12) and (ii) has a signal light output (18) which is spaced apart from the signal light input, (b) a signal light Brillouin amplifier (20) (i) a signal light amplification pump pump (22) configured to generate signal light amplification pump light (24) which (ii) is arranged to amplify the signal light (12) by means of stimulated Brillouin scattering and (iii) comprises a signal light amplification pump light coupler for coupling the signal light amplification pump light (24) into the optical fiber (14), characterized by (c) a signal light polarization adjuster (38) configured to adjust a signal light polarization (P12) of the signal light (12) incident through the signal light input (16) to a predetermined signal light target polarization (Pi2,soii) and / or (d) a rear light polarization adjuster (28) configured to adjust a rear light polarization (PR) of the rear light (30) incident through the signal light output (18) such that the rear light polarization (P ) corresponds to a signal light polarization (Ps) of the signal light (12).
2. Optical amplifier according to claim 1, characterized in that the signal light polarization (P12) corresponds to the rear light polarization (PR).
3. Optical amplifier according to one of the preceding claims, characterized by a signal light polarization meter (36) for determining the signal light polarization (Ps).
4. Optical amplifier according to one of the preceding claims, characterized by a rear light Brillouin amplifier, which (a) a rear light booster pump generator (54) configured to produce rear light booster pump light (52), and (b) is arranged to enhance the rear light (30) by means of stimulated Brillouin scattering and (c) comprises a taillight booster pump light coupler (26) for coupling the taillight booster pump light (24) into the optical fiber (14).
5. Optical amplifier according to one of the preceding claims, characterized by (a) a rear light pumping light frequency modulator for changing a rear light pumping light frequency (VB) of the rear light boosting pumping light (52), (b) a rear light intensity meter (59) for measuring a rear light intensity of the rear light (30), which is arranged in the rear light propagation direction in front of the rear light amplification pump light coupler, and (c) a taillight frequency control connected to the taillight booster pumping frequency modulator and the taillight intensity meter (59) for controlling the taillight pumping frequency (VB) to maximum taillight intensity.
6. Optical amplifier according to one of the preceding claims, characterized in that (a) the signal light Brillouin amplifier (20) comprises a Brillouin frequency detection device for time-dependent detection of a Brillouin frequency (VBFS) at which the signal light is maximally amplified, wherein the Brillouin frequency detection device is connected to the signal light amplification pump (22) for setting the signal light pump frequency (VF), wherein (b) the Brillouin frequency detection device (i) a signal light amplification pump light frequency modulator (56) for changing a signal light pump light frequency (VF) of the signal light pump light, (ii) a signal light intensity meter (58) for measuring a signal light intensity of the signal light (12) in the signal light propagation direction, which is arranged in front of the signal light amplification pump light coupler, and (iii) a signal light frequency control system connected to the signal light amplification pump light frequency modulator (56) and the signal light intensity meter (58) for controlling the signal light pump light frequency to maximum signal light intensity.
7. Optical amplifier according to one of the preceding claims, characterized by a pump laser polarization adjustment device (60) configured for controlling or regulating a rear light amplification pump light polarization (P52) of the rear light amplification pump light (52) and / or a signal light amplification pump light polarization (P 24 ) of the signal light amplification pump light (24), so that these polarizations correspond to each other in the optical fiber (14).
8. Optical amplifier according to one of the preceding claims, characterized by a rear light polarization adjustment device (62) configured for controlling or regulating a rear light amplification pump light polarization (P52) of the rear light amplification pump light (52).
9. Optical amplifier according to one of the preceding claims, characterized by a signal light pump laser polarization matching device (60) configured for controlling and regulating a signal light amplification pump light polarization. (P52, P24) of the signal light amplification pump light (24), so that these polarizations in the optical fiber (14) correspond to each other at the coupler (26). Optical amplifier according to one of the preceding claims, characterized in that (a) the signal light Brillouin amplifier (20) comprises a signal light phase stabilization device which includes a high-frequency photodiode (44), and that (b) the high-frequency photodiode is arranged to detect a beat frequency (fbi) between a signal light frequency (vs) of the signal light (12) and the signal light pumping frequency (VF). Optical amplifier according to one of the preceding claims, characterized by (a) a beam splitter (26) with (i) a signal light input port connected to the signal light input (16), in particular the signal light polarization sensor (36), (ii) a rear light input connected to the signal light output (18), in particular the rear light polarization switch (28), (iii) a signal light amplification pump light input connected to the signal light amplification pump (54), and (iv) a rear light boost pump light input connected to the rear light boost pump (54), and (b) a circulator (48) which (i) is connected to a first port (p1) with the beam splitter (26), (ii) is connected to a second port (p2) with the rear light boost pump (54) and (iii) is connected to a third port (p3) with the low-frequency photodiode (50). Optical amplifier according to any one of the preceding claims 1 to 10, characterized in that the optical amplifier (a) a signal light amplification pump light cavity or a signal light amplification pump light boost cavity (64) comprising (i) a highly reflective signal light amplification pump light coupling element (68.1) and (ii) comprises a first optical insulator (70), (iii) wherein the signal light (12) strikes the signal light amplification pump light coupling element at an angle of incidence to a normal, and (b) a rear light amplification pump light cavity or a rear light amplification Pump light booster cavity (66), which (i) a highly reflective rear light booster pump light coupling element (68.2) and, (ii) has a second optical insulator (70.2), (iii) wherein the rear light (30) strikes the rear light coupling element at an angle of incidence to a normal. Optical network (76) with (a) a frequency source (78) for emitting signal light, (b) a frequency receiver (80), (c) an optical fiber (82) from the frequency source (78) to the frequency receiver (80), (d) at least one optical amplifier (10) according to any one of the preceding claims, which (i) is arranged between the frequency source (78) and the frequency receiver (80), (ii) a signal light input (16) for coupling in the signal light (12) and (iii) has a signal light output (18) which is spaced apart from the signal light input (16), (iv) a signal light amplification pump (22) configured to generate signal light amplification pump light (24), (v) which is arranged to amplify the signal light (12) by means of stimulated Brillouin scattering and (vi) has a signal light amplification pump light coupler for coupling the signal light amplification pump light (24) into the optical fiber (14), (e) a rear light polarization adjuster (28) configured to adjust a rear light polarization corresponding to a signal light polarization of the signal light (12) and / or (f) a signal light polarization adjuster (38) configured to adjust the signal light polarization of the signal light (12) to a predetermined signal light target polarization (Pi2, S0 n).