A wavelength-tuned non-local dispersion compensation method and apparatus

Abstract

The application discloses a wavelength-tunable non-local dispersion compensation device, comprising: a laser; a waveguide connected to the laser, used for exciting the waveguide by the continuous laser to generate a pair of preset-wavelength and mutually-perpendicular polarization photons, wherein the preset wavelength is obtained according to a dispersion compensation formula; a polarization beam splitter connected to the waveguide, having a first output end and a second output end, used for dividing the polarization photons into signal photons and idler photons to be output from the first output end and the second output end respectively; a first single-photon detector and a second single-photon detector; and a time-correlated single-photon counter, used for measuring the width of the time-domain coincidence peak of the signal photons output by the first single-photon detector and the idler photons output by the second single-photon detector to evaluate the dispersion compensation effect. The application adjusts the wavelength to compensate the dispersion, can realize the dynamic adjustment of the dispersion without replacing the dispersion compensation module, and does not need to interrupt the fiber link, thereby enhancing the system stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of quantum information, and particularly relates to a wavelength-tuned non-local dispersion compensation method and device. BACKGROUND

[0002] Group velocity dispersion refers to the change of the transmission speed of light waves with the difference of the frequency of incident light, which is a main factor affecting the performance of optical systems. For example, when laser pulses interact with nonlinear crystals, the peak power of the dispersion broadened pulses decreases, thereby limiting the nonlinear conversion efficiency. In addition, in the field of optical fiber communication, dispersion is also a problem that needs to be focused on. Due to the existence of optical fiber dispersion, the optical signal pulses transmitted through the optical fiber are distorted; when the dispersion is serious, the optical pulses overlap with each other, causing inter-symbol interference and increasing the bit error rate. Dispersion not only affects the transmission capacity of optical fibers, but also limits the relay distance of optical fiber communication systems. Therefore, it is necessary to take dispersion compensation technology to compensate for dispersion, and the basic idea is to add dispersion of the opposite sign in the system to offset the influence of the original dispersion.

[0003] In practical applications, taking widely laid telecommunication single-mode optical fiber links as an example, the dispersion of the optical transmission link is related to the length of the link passed through, and different types of dispersion compensation modules need to be selected to achieve precise dispersion compensation for different link lengths.

[0004] However, the above existing application needs to select different types of dispersion compensation modules according to the characteristics of the link, so that after the link is adjusted, the appropriate dispersion compensation module needs to be replaced, and the frequent replacement of the module not only affects the work efficiency and causes resource waste, but also needs to disconnect the optical fiber link during replacement, affecting the system working stability. SUMMARY

[0005] In order to solve the above problems existing in the prior art, the present application provides a wavelength-tuned non-local dispersion compensation method and device. The technical problems to be solved by the present application are solved by the following technical solutions:

[0006] A wavelength-tuned non-local dispersion compensation device, comprising:

[0007] A laser for generating continuous laser;

[0008] A waveguide connected to the laser for exciting the waveguide by the continuous laser to generate a pair of polarization photons of a preset wavelength and perpendicular to each other, wherein the preset wavelength is obtained according to a dispersion compensation formula;

[0009] A polarization beam splitter connected to the waveguide and having a first output end and a second output end, for dividing the polarization photons into signal photons and idler photons and outputting them from the first output end and the second output end, respectively.

[0010] The first single-photon detector is connected to the first output end of the polarization beam splitter via a first optical fiber;

[0011] The second single-photon detector is connected to the second output end of the polarization beam splitter via a second optical fiber;

[0012] A time-correlated single-photon counter is used to measure the width of the temporal coincidence peak of the signal photon output by the first single-photon detector and the idle photon output by the second single-photon detector in order to evaluate the dispersion compensation effect.

[0013] In one specific embodiment, it further includes: a temperature controller for controlling the waveguide temperature so that the wavelength of the generated polarized photons is the preset wavelength.

[0014] In one specific implementation, the wavelength of the signal photon changes by 0.5 nm for every 1°C change in the waveguide temperature.

[0015] In one specific embodiment, the length of the second optical fiber is determined by the length of the first optical fiber.

[0016] In one specific embodiment, the first optical fiber is a 50km long single-mode optical fiber.

[0017] In one specific embodiment, the second optical fiber is a dispersion-compensated optical fiber with a length of 6.2 km.

[0018] In one specific embodiment, the dispersion compensation formula is:

[0019]

[0020] Where B and C are single-mode fiber parameters, B = 0.016, C = 6.56 × 10⁻⁶. 10 ;λ p λ is the pump light wavelength; s η is the wavelength of the signal photon, and η is the matching factor.

[0021] This invention also provides a wavelength-tuned nonlocal dispersion compensation method, comprising:

[0022] Generate continuous laser light;

[0023] A pair of mutually perpendicular polarized photons with a preset wavelength are generated by the continuous laser-excited waveguide, wherein the preset wavelength is obtained according to the dispersion compensation formula;

[0024] The dispersion compensation formula is as follows:

[0025]

[0026] Where B and C are single-mode fiber parameters, B = 0.016, C = 6.56 × 10⁻⁶. 10 ;λ p λ is the pump light wavelength; s η is the wavelength of the signal photon, and η is the matching factor.

[0027] The beneficial effects of this invention are:

[0028] The wavelength-tuned nonlocal dispersion compensation device provided by this invention performs dispersion compensation by adjusting the wavelength. It can achieve dynamic adjustment of dispersion without replacing the dispersion compensation module and without interrupting the optical fiber link, thereby enhancing system stability.

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a wavelength-tuned nonlocal dispersion compensation device provided in an embodiment of the present invention;

[0031] Figure 2 This is a diagram showing the relationship between the total system dispersion and the wavelength of the signal photon provided in this embodiment of the invention.

[0032] Figure 3 This is a graph showing the relationship between the signal light wavelength and the coincidence width provided in an embodiment of the present invention. Detailed Implementation

[0033] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0034] Example 1

[0035] Please see Figure 1 , Figure 1 This is a schematic diagram of a wavelength-tuned nonlocal dispersion compensation device according to an embodiment of the present invention, comprising:

[0036] Laser 1 is used to generate continuous laser light; the laser in this embodiment can be a DBR (distributed Bragg reflector) laser.

[0037] Waveguide 2, connected to the laser 1, is used to excite the waveguide to generate a pair of mutually perpendicular polarized photons with a preset wavelength, wherein the preset wavelength is obtained according to the dispersion compensation formula;

[0038] The waveguide can be a lithium niobate (PPLN) waveguide, and in a preferred embodiment, the wavelength of the photon can be adjusted by regulating the temperature of the waveguide.

[0039] Preferably, it further includes: a temperature controller 3, used to control the waveguide temperature so that the wavelength of the generated polarized photons is the preset wavelength. This ensures that for every 1°C change in the waveguide temperature, the wavelength of the signal photons changes by 0.5 nm.

[0040] Polarization beam splitter 4, connected to waveguide 3, has a first output end and a second output end, used to split the polarized photon into signal photon and idle photon and output them from the first output end and the second output end respectively;

[0041] The first single-photon detector 7 is connected to the first output end of the polarization beam splitter 4 via the first optical fiber 5;

[0042] The second single-photon detector 8 is connected to the second output end of the polarization beam splitter 4 via the second optical fiber 6;

[0043] The time-correlated single-photon counter 9 is used to measure the width of the temporal coincidence peak of the signal photon output by the first single-photon detector 7 and the idle photon output by the second single-photon detector 8 in order to evaluate the dispersion compensation effect.

[0044] The length of the second optical fiber is determined by the length of the first optical fiber. Specifically, the first optical fiber 5 is a 50km long single-mode optical fiber. The second optical fiber 6 is a 6.2km long dispersion-compensating optical fiber.

[0045] In one specific embodiment, the dispersion compensation formula is:

[0046]

[0047] Where B and C are single-mode fiber parameters; taking the fiber mentioned above as an example, B = 0.016 and C = 6.56 × 10⁻⁶. 10 ;λ p λ is the pump light wavelength; s η is the wavelength of the signal photon, and η is the matching factor.

[0048] The derivation of the above dispersion compensation formula is as follows:

[0049] The dispersion of standard telecommunications single-mode fiber (SMF) is related to wavelength (λ) as follows:

[0050] D SMF (λ)=2(Bλ-Cλ -3 ),

[0051] Parameters B and C are related to the fiber characteristics. Typically, the dispersion compensation module (DCM) has a good dispersion matching slope with the single-mode fiber. Considering the matching factor η due to length mismatch, the relationship between the dispersion of the dispersion compensation module and wavelength is as follows:

[0052] D DCM (λ)=-2η(Bλ-Cλ -3 ).

[0053] Under non-local dispersion compensation conditions, the single-mode fiber and the dispersion compensation module transmit signal photons and idle photons respectively. The total system dispersion is the sum of the dispersion introduced by the single-mode fiber and the dispersion compensation module:

[0054]

[0055] When the two photons used have frequency anticorrelation characteristics, the idle photon wavelength λ i It can be determined by the pump light wavelength λ p and the signal photon wavelength λ s Indicates, that is At this point, the total dispersion of the system can be determined by the wavelength of the signal photon (λ). s )express:

[0056]

[0057] This implementation uses a 50km single-mode fiber as an example for compensation. Substituting the single-mode fiber parameters (B = 0.016, C = 6.56 × 10⁻⁶),... 10 ), at pump light wavelength λ p Numerical simulations were performed at a wavelength of 780 nm to obtain the relationship between the total system dispersion and the signal photon wavelength, as shown below. Figure 2 As shown, by adjusting the wavelength of the signal photon, the total dispersion of the system can be continuously adjusted from negative to positive. For a two-photon source generated based on the spontaneous parametric downconversion effect, its wavelength characteristics depend on the phase-matching condition of the nonlinear crystal. Periodically polarized crystals, as one of the most commonly used crystals, have phase-matching conditions that are temperature-dependent; therefore, changing the crystal temperature can achieve wavelength tuning of the photon.

[0058] To verify the effectiveness of this embodiment, the PPLN waveguide was modified while the change in coincidence width was recorded as follows: Figure 3 As shown, when the signal light wavelength is set to 1565.7 nm, the minimum coincidence width is 86.1 ps, which is very close to the jitter limit of the detection system, indicating that the optimal dispersion compensation effect can be achieved by adjusting the signal light wavelength. Similarly, after extending the length of single-mode fiber 5 to 60 km and repeating the above wavelength adjustment and coincidence measurement process, a minimum coincidence width of 88.2 ps can be obtained, with a corresponding PPLN temperature of 52 °C.

[0059] In this embodiment, for every 1 nm change in photon wavelength, the dispersion change is approximately 10 ps. Considering that the dispersion coefficient of a standard single-mode fiber is approximately 17 ps / nm km, a wavelength change of 1.7 nm can compensate for a single-mode fiber length of 1 km. Generally speaking, the wavelength adjustment range of photons generated based on spontaneous parametric downconversion can reach over 20 nm, corresponding to a detuning amount that can be compensated for exceeding 10 km of fiber length.

[0060] This invention also provides a wavelength-tuned nonlocal dispersion compensation method, comprising:

[0061] Generate continuous laser light;

[0062] A pair of mutually perpendicular polarized photons with a preset wavelength are generated by the continuous laser-excited waveguide, wherein the preset wavelength is obtained according to the dispersion compensation formula;

[0063] The dispersion compensation formula is as follows:

[0064]

[0065] Where B and C are single-mode fiber parameters, B = 0.016, C = 6.56 × 10⁻⁶. 10 ;λ p λ is the pump light wavelength; s η is the wavelength of the signal photon, and η is the matching factor.

[0066] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0067] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0068] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A wavelength-tuned nonlocal dispersion compensation device, characterized in that, include: Lasers are used to generate continuous laser light. A waveguide, connected to the laser, is used to excite the waveguide to generate a pair of mutually perpendicular polarized photons with a preset wavelength, wherein the preset wavelength is obtained according to a dispersion compensation formula; A polarization beam splitter, connected to the waveguide, has a first output end and a second output end, used to split the polarized photons into signal photons and idle photons, which are output from the first output end and the second output end, respectively. The first single-photon detector is connected to the first output end of the polarization beam splitter via a first optical fiber; The second single-photon detector is connected to the second output end of the polarization beam splitter via a second optical fiber; A time-correlated single-photon counter is used to measure the width of the temporal coincidence peak of the signal photon output by the first single-photon detector and the idle photon output by the second single-photon detector in order to evaluate the dispersion compensation effect. The length of the second optical fiber is determined by the first optical fiber, wherein the first optical fiber is a single-mode optical fiber and the second optical fiber is a dispersion-compensating optical fiber; The dispersion compensation formula is as follows: ； Where B and C are single-mode fiber parameters, B=0.016, C= ; The pump light wavelength; The wavelength of the signal photon. This is the matching factor.

2. The wavelength-tuned nonlocal dispersion compensation device according to claim 1, characterized in that, Also includes: A temperature controller is used to control the waveguide temperature so that the wavelength of the generated polarized photons is the preset wavelength.

3. The wavelength-tuned nonlocal dispersion compensation device according to claim 2, characterized in that, This results in a 0.5 nm change in the signal photon wavelength for every 1°C change in the waveguide temperature.

4. The wavelength-tuned nonlocal dispersion compensation device according to claim 1, characterized in that, The first optical fiber is a 50km long single-mode optical fiber.

5. The wavelength-tuned nonlocal dispersion compensation device according to claim 1, characterized in that, The second optical fiber is a dispersion-compensated optical fiber with a length of 6.2 km.

6. A nonlocal dispersion compensation method based on wavelength tuning, characterized in that, An application to the wavelength-tuned nonlocal dispersion compensation device as described in any one of claims 1-5, comprising: Generate continuous laser light; A pair of mutually perpendicular polarized photons with a preset wavelength are generated by the continuous laser-excited waveguide, wherein the preset wavelength is obtained according to the dispersion compensation formula; The dispersion compensation formula is as follows: ； Where B and C are single-mode fiber parameters, B=0.016, C= ; The pump light wavelength; The wavelength of the signal photon. This is the matching factor.

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