WO2024078374A1 - 一种tosa、光模块、光网络设备和光发射方法 - Google Patents

一种tosa、光模块、光网络设备和光发射方法 Download PDF

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Publication number
WO2024078374A1
WO2024078374A1 PCT/CN2023/123139 CN2023123139W WO2024078374A1 WO 2024078374 A1 WO2024078374 A1 WO 2024078374A1 CN 2023123139 W CN2023123139 W CN 2023123139W WO 2024078374 A1 WO2024078374 A1 WO 2024078374A1
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WIPO (PCT)
Prior art keywords
light beam
polarization
polarization state
combined
polarization rotation
Prior art date
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PCT/CN2023/123139
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English (en)
French (fr)
Inventor
廖浩
李志伟
田雨
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华为技术有限公司
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Publication of WO2024078374A1 publication Critical patent/WO2024078374A1/zh

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
    • G02B6/4213—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms the intermediate optical elements being polarisation selective optical elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/27—Optical coupling means with polarisation selective and adjusting means
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/27—Optical coupling means with polarisation selective and adjusting means
    • G02B6/2746—Optical coupling means with polarisation selective and adjusting means comprising non-reciprocal devices, e.g. isolators, FRM, circulators, quasi-isolators
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/4201—Packages, e.g. shape, construction, internal or external details
    • G02B6/4204—Packages, e.g. shape, construction, internal or external details the coupling comprising intermediate optical elements, e.g. lenses, holograms
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/42—Coupling light guides with opto-electronic elements
    • G02B6/43—Arrangements comprising a plurality of opto-electronic elements and associated optical interconnections

Definitions

  • the present application relates to the field of communications, and in particular to a TOSA, an optical module, an optical network device and an optical transmission method.
  • the transmission bandwidth and distance requirements of optical modules are getting higher and higher.
  • the current 800G (single-wavelength 200Gbps) intensity modulation/direct detection (IM/DD) module is the focus of research.
  • the 800G 2km multi-source agreement (MSA) has been released.
  • MSA Local Area Network-Wavelength Division Multiplexing
  • LAN-WDM Local Area Network-Wavelength Division Multiplexing
  • FWM Four Wave Mixing
  • FWM is a nonlinear phenomenon in optical fiber.
  • the FWM effect will generate a new wavelength, called idler light. If the idler light falls within the band of the service light, it will introduce additional noise.
  • the existing technology does not provide the most effective solution to reduce the impact of FWM.
  • the embodiments of the present application provide a TOSA, an optical module, an optical network device, and an optical transmission method, which can effectively reduce the impact of FWM.
  • an embodiment of the present application provides a transmitting optical sub-assembly (TOSA).
  • the TOSA includes: four light sources, a polarization rotation unit and a combining unit.
  • the four light sources are used to respectively emit four light beams.
  • the four light beams have the same initial polarization state and the wavelengths of the four light beams are different.
  • the four light beams are, in descending order of wavelength, a first light beam, a second light beam, a third light beam and a fourth light beam.
  • the polarization rotation unit is used to adjust the polarization state of at least two light beams so that the first polarization state of the first light beam and the fourth light beam is perpendicular to the second polarization state of the second light beam and the third light beam.
  • the combining unit is used to combine the four light beams output by the polarization rotation unit to obtain a combined light beam.
  • a polarization interleaved emission scheme is provided. Taking the initial polarization state of the four-way light beam as "XXXX” as an example, the polarization state of the output light beam of the combining unit is "XYYX", where "X" and "Y” represent two polarization states perpendicular to each other.
  • the polarization interleaved emission method designed in this application can effectively reduce the impact of FWM.
  • the initial polarization state of the four light beams is the first polarization state
  • the polarization rotation unit is used to adjust the second light beam and the third light beam to the second polarization state.
  • the initial polarization state of the four light beams is the second polarization state
  • the polarization rotation unit is used to adjust the first light beam and the fourth light beam to the first polarization state.
  • the polarization rotation unit includes a first polarization rotation element and a second polarization rotation element. If the initial polarization state of the four light beams is the first polarization state, the first polarization rotation element is used to adjust the second light beam to the second polarization state, and the second polarization rotation element is used to adjust the third light beam to the second polarization state. If the initial polarization state of the four light beams is the second polarization state, the first polarization rotation element is used to adjust the first light beam to the first polarization state, and the second polarization rotation element is used to adjust the fourth light beam to the first polarization state.
  • the TOSA further includes a polarization-independent isolator, and the polarization-independent isolator is used to transmit the combined light beam and isolate an echo reflected light beam of the combined light beam.
  • the polarization rotation unit is used to adjust the first light beam and the fourth light beam from an initial polarization state to a first polarization state, and adjust the second light beam and the third light beam from an initial polarization state to a second polarization state.
  • the polarization rotation unit includes two first polarization rotation elements and two second polarization rotation elements.
  • the two first polarization rotation units are used to adjust the first light beam and the fourth light beam from an initial polarization state to a first polarization state, respectively; and the two second polarization rotation elements are used to adjust the second light beam and the third light beam from an initial polarization state to a second polarization state, respectively.
  • the two first polarization rotation units are first polarization-dependent isolators, and the two second polarization rotation units are second polarization-dependent isolators.
  • the two first polarization rotation units are also used to respectively isolate the echo reflected beam of the first light beam and the echo reflected beam of the fourth light beam.
  • the two second polarization rotation units are also used to respectively isolate the echo reflected beam of the second light beam and the echo reflected beam of the third light beam.
  • the wave combining unit is a z-block wave combiner.
  • each light source includes a laser and a collimating lens, and the collimating lens is used to collimate the light beam emitted by the laser.
  • an embodiment of the present application provides a TOSA.
  • the TOSA includes: four light sources, a first combining unit, a polarization rotation unit, and a second combining unit.
  • the four light sources are used to emit four light beams respectively. Among them, the four light beams have the same initial polarization state and the wavelengths of the four light beams are different.
  • the four light beams are, in descending order of wavelength, a first light beam, a second light beam, a third light beam, and a fourth light beam.
  • the first combining unit is used to combine the first light beam and the fourth light beam to obtain a first combined light beam, and to combine the second light beam and the third light beam to obtain a second combined light beam.
  • the polarization rotation unit is used to adjust the polarization state of at least one of the first combined light beam and the second combined light beam, so that the first polarization state of the first combined light beam is perpendicular to the second polarization state of the second combined light beam.
  • the second combining unit is used to combine the first combined light beam and the second combined light beam output by the polarization rotation unit to obtain a third combined light beam.
  • a polarization interleaved emission scheme is provided. Taking the initial polarization state of the four-way light beam as "XXXX” as an example, the polarization state of the output light beam of the combining unit is "XYYX", where "X" and "Y” represent two polarization states perpendicular to each other.
  • the polarization interleaved emission method designed in this application can effectively reduce the impact of FWM.
  • the polarization rotation unit includes a polarization rotation element and a polarization-dependent isolator.
  • the polarization-dependent isolator is used to transmit the first combined light beam and the second combined light beam, and to isolate the echo reflected light beam of the first combined light beam and the echo reflected light beam of the second combined light beam. If the initial polarization state of the four-way light beam is the first polarization state, the polarization rotation element is used to adjust the second combined light beam output by the polarization-dependent isolator to the second polarization state. If the initial polarization state of the four-way light beam is the second polarization state, the polarization rotation element is used to adjust the first combined light beam output by the polarization-dependent isolator to the first polarization state.
  • the polarization rotation unit includes a first polarization rotation element and a second polarization rotation element.
  • the first polarization rotation element is used to adjust the first combined light beam from an initial polarization state to a first polarization state.
  • the second polarization rotation element is used to adjust the second combined light beam from an initial polarization state to a second polarization state.
  • the first polarization rotation element is a first polarization-dependent isolator
  • the second polarization rotation element is a second polarization-dependent isolator.
  • the first polarization rotation element is also used to isolate the echo reflected beam of the first combined light beam.
  • the second polarization rotation element is also used to isolate the echo reflected beam of the second combined light beam.
  • the first combining unit includes a reflecting element, a first combining element, and a second combining element.
  • the reflecting element is used to reflect the first light beam and the second light beam.
  • the first combining element is used to combine the reflected first light beam and the fourth light beam to obtain a first combined light beam.
  • the second combining element is used to combine the reflected second light beam and the third light beam to obtain a second combined light beam.
  • the reflecting element is used to reflect the third light beam and the fourth light beam.
  • the first combining element is used to combine the first light beam and the reflected fourth light beam to obtain a first combined light beam.
  • the second combining element is used to combine the second light beam and the reflected third light beam to obtain a second combined light beam.
  • the second beam combiner unit is a polarization beam combiner (PBC).
  • PBC polarization beam combiner
  • each light source includes a laser and a collimating lens, and the collimating lens is used to collimate the light beam emitted by the laser.
  • an embodiment of the present application provides an optical module.
  • the optical module includes a TOSA, a receiving optical sub-assembly (ROSA), and an optical fiber connection port as described in any embodiment of the first aspect and the second aspect above.
  • the TOSA is used to output a light beam to the optical fiber connection port.
  • the ROSA is used to receive a light beam from the optical fiber connection port.
  • an embodiment of the present application provides an optical network device, which includes the optical module described in the third aspect, and the optical module is integrated in the optical network device.
  • an embodiment of the present application provides a light emission method, which is applied to a light emission module TOSA, and the TOSA includes: four light sources, a polarization rotation unit and a wave combining unit.
  • the method includes: emitting four light beams respectively through four light sources.
  • the four light beams have the same initial polarization state and the wavelengths of the four light beams are different.
  • the four light beams are, in descending order of wavelength, a first light beam, a second light beam, a third light beam and a fourth light beam.
  • the polarization state of at least two light beams is adjusted by the polarization rotation unit so that the first light beam and the fourth light beam are The first polarization state of the light beam is perpendicular to the second polarization states of the second light beam and the third light beam.
  • the four light beams output by the polarization rotation unit are combined by the combining unit to obtain a combined light beam.
  • the initial polarization state of the four light beams is the first polarization state
  • adjusting the polarization state of at least two light beams by the polarization rotation unit includes: adjusting the second light beam and the third light beam to the second polarization state by the polarization rotation unit.
  • the initial polarization state of the four light beams is the second polarization state
  • adjusting the polarization state of at least two light beams by the polarization rotation unit includes: adjusting the first light beam and the fourth light beam to the first polarization state by the polarization rotation unit.
  • the polarization rotation unit includes a first polarization rotation element and a second polarization rotation element
  • adjusting the polarization state of at least two light beams by the polarization rotation unit includes: if the initial polarization state of the four light beams is the first polarization state, adjusting the second light beam to the second polarization state by the first polarization rotation element, and adjusting the third light beam to the second polarization state by the second polarization rotation element. If the initial polarization state of the four light beams is the second polarization state, adjusting the first light beam to the first polarization state by the first polarization rotation element, and adjusting the fourth light beam to the first polarization state by the second polarization rotation element.
  • the TOSA further includes a polarization-independent isolator
  • the method further includes: transmitting the combined light beam through the polarization-independent isolator and isolating an echo reflected light beam of the combined light beam.
  • adjusting the polarization state of at least two light beams by a polarization rotation unit includes: adjusting the first light beam and the fourth light beam from an initial polarization state to a first polarization state, and adjusting the second light beam and the third light beam from an initial polarization state to a second polarization state by the polarization rotation unit.
  • the polarization rotation unit includes two first polarization rotation elements and two second polarization rotation elements
  • adjusting the polarization state of at least two light beams by the polarization rotation unit includes: adjusting the first light beam and the fourth light beam from an initial polarization state to a first polarization state by the two first polarization rotation units, respectively.
  • the two first polarization rotation units are first polarization-dependent isolators
  • the two second polarization rotation units are second polarization-dependent isolators
  • the method further includes: isolating the echo reflected beam of the first light beam and the echo reflected beam of the fourth light beam respectively by the two first polarization rotation units, and isolating the echo reflected beam of the second light beam and the echo reflected beam of the third light beam respectively by the two second polarization rotation units.
  • an embodiment of the present application provides a light emission method, which is applied to a light emission module TOSA, and the TOSA includes: four light sources, a first wave combining unit, a polarization rotation unit, and a second wave combining unit.
  • the method includes: emitting four light beams respectively through four light sources.
  • the four light beams have the same initial polarization state and the wavelengths of the four light beams are different.
  • the four light beams are, in descending order of wavelength, a first light beam, a second light beam, a third light beam, and a fourth light beam.
  • the first light beam and the fourth light beam are combined by the first wave combining unit to obtain a first combined light beam, and the second light beam and the third light beam are combined to obtain a second combined light beam.
  • the polarization state of at least one of the first combined light beam and the second combined light beam is adjusted by the polarization rotation unit so that the first polarization state of the first combined light beam is perpendicular to the second polarization state of the second combined light beam.
  • the first combined light beam and the second combined light beam output by the polarization rotation unit are combined by the second wave combining unit to obtain a third combined light beam.
  • the polarization rotation unit includes a polarization rotation element and a polarization-dependent isolator, and adjusting the polarization state of at least one of the first combined light beam and the second combined light beam by the polarization rotation unit includes: transmitting the first combined light beam and the second combined light beam through the polarization-dependent isolator, and isolating the echo reflected light beam of the first combined light beam and the echo reflected light beam of the second combined light beam. If the initial polarization state of the four-way light beam is the first polarization state, the second combined light beam output by the polarization-dependent isolator is adjusted to the second polarization state by the polarization rotation element. If the initial polarization state of the four-way light beam is the second polarization state, the first combined light beam output by the polarization-dependent isolator is adjusted to the first polarization state by the polarization rotation element.
  • the polarization rotation unit includes a first polarization rotation element and a second polarization rotation element, and adjusting the polarization state of at least one of the first combined light beam and the second combined light beam by the polarization rotation unit includes: adjusting the first combined light beam from an initial polarization state to a first polarization state by the first polarization rotation element, and adjusting the second combined light beam from an initial polarization state to a second polarization state by the second polarization rotation element.
  • the first polarization rotation element is a first polarization-dependent isolator
  • the second polarization rotation element is a second polarization-dependent isolator
  • the method further includes: isolating the echo reflected beam of the first combined beam by the first polarization rotation element, and isolating the echo reflected beam of the second combined beam by the second polarization rotation element.
  • the first wave combining unit includes a reflective element, a first wave combining element, and a second wave combining element.
  • the combining unit combines the first light beam and the fourth light beam to obtain the first combined light beam, and combines the second light beam and the third light beam to obtain the second combined light beam, including: reflecting the first light beam and the second light beam through a reflective element; combining the reflected first light beam and the fourth light beam through the first combining element to obtain the first combined light beam; combining the reflected second light beam and the third light beam through the second combining element to obtain the second combined light beam.
  • the third light beam and the fourth light beam are reflected through a reflective element; combining the first light beam and the reflected fourth light beam through the first combining element to obtain the first combined light beam; combining the second light beam and the reflected third light beam through the second combining element to obtain the second combined light beam.
  • four light sources in the TOSA output four light beams with the same initial polarization state and different wavelengths.
  • the polarization rotation unit adjusts the polarization state of at least two of the light beams, so that the first polarization state of the first light beam and the fourth light beam is perpendicular to the second polarization state of the second light beam and the third light beam.
  • the combining unit combines the four light beams output by the polarization rotation unit and outputs the combined light beam. It should be understood that the present application provides a solution for polarization interleaved transmission.
  • the polarization state of the light beam output by the combining unit is "XYYX", where "X" and "Y” represent two polarization states perpendicular to each other.
  • the polarization interleaved transmission method designed in the present application can effectively reduce the impact of FWM.
  • the polarization interleaved transmission scheme provided in the present application is more helpful in reducing the interference of idle light on business light.
  • FIG1 is a schematic diagram showing a simulation comparison of FWM costs using different light emission modes
  • FIG2 is a schematic diagram of the simulation of the relationship between the idler light intensity and the zero dispersion wavelength of the optical fiber using the "XYYX" mode of FWM;
  • FIG3 is a schematic diagram of a first structure of a TOSA in an embodiment of the present application.
  • FIG4( a ) is a schematic diagram of a second structure of a TOSA in an embodiment of the present application.
  • FIG4( b ) is a schematic diagram of a third structure of a TOSA in an embodiment of the present application.
  • FIG5 is a schematic diagram of a fourth structure of a TOSA according to an embodiment of the present application.
  • FIG6 is a schematic diagram of a fifth structure of a TOSA in an embodiment of the present application.
  • FIG. 7( a ) is a sixth structural diagram of a TOSA in an embodiment of the present application.
  • FIG. 7( b ) is a schematic diagram of a seventh structure of a TOSA in an embodiment of the present application.
  • FIG8 is a schematic diagram of an eighth structure of a TOSA in an embodiment of the present application.
  • FIG9 is a ninth structural diagram of a TOSA in an embodiment of the present application.
  • FIG10 is a schematic diagram of the tenth structure of a TOSA in an embodiment of the present application.
  • FIG11 is a schematic diagram of the eleventh structure of a TOSA in an embodiment of the present application.
  • FIG12 is a schematic diagram of an embodiment of a light emission method provided in an embodiment of the present application.
  • FIG. 13 is a schematic diagram of another light emission method provided in an embodiment of the present application.
  • the embodiments of the present application provide a TOSA, an optical module, an optical network device and an optical transmission method, which can effectively reduce the impact of FWM.
  • the terms “first”, “second”, “third”, “fourth”, etc. (if any) in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments described here can be implemented in an order other than that illustrated or described here.
  • the embodiments of the present application can be mainly applied to optical communication scenarios, such as optical networks for optical interconnection of data centers.
  • the optical module is responsible for the photoelectric conversion and transmission of network signals, and is the basis for the normal communication of the entire network.
  • the optical module includes an optical transmitting module (Transmitting Optical sub-assembly, TOSA) and an optical receiving module (Receiving Optical sub-assembly, ROSA).
  • TOSA is used to convert electrical signals into optical signals and transmit the optical signals to optical fibers.
  • ROSA is used to receive optical signals from optical fibers and convert the optical signals into electrical signals.
  • TOSA will use wavelength division multiplexing (WDM) technology to combine two or more optical carrier signals of different wavelengths through a multiplexer (also called a combiner) to obtain a combined signal.
  • WDM wavelength division multiplexing
  • the wave signal passes through a demultiplexer (also called a wavelength splitter or demultiplexer) to separate the optical carriers of various wavelengths, and then further processed to restore the original signal.
  • demultiplexer also called a wavelength splitter or demultiplexer
  • FWM four-wave mixing
  • an embodiment of the present application provides a TOSA that can achieve polarization interleaved emission, which helps to reduce the impact of FWM.
  • the four light beams emitted by four light sources have the same original polarization state.
  • the four original polarization state light beams are recorded as "XXXX”.
  • the TOSA makes the polarization state of the four light beams finally output to the optical fiber recorded as "XYYX".
  • "X" and "Y” represent two polarization states that are perpendicular to each other.
  • Figure 1 is a simulation comparison diagram of the FWM cost using different optical emission modes.
  • the horizontal axis represents the fiber optical power (in dBm)
  • the vertical axis represents the FWM cost (in dB), where the FWM cost can be understood as the noise level introduced due to the influence of FWM.
  • the FWM cost can be understood as the noise level introduced due to the influence of FWM.
  • the fiber optical power corresponding to the "XXXX" mode is about 1dBm
  • the fiber optical power corresponding to the "XYXY” mode is about 5dBm
  • the fiber optical power corresponding to the "XYYX” mode is about 11dBm.
  • the fiber optical power of the "XYYX” mode is the highest and the effect is the best. In other words, when the fiber optical power is consistent, the FWM cost of the "XYYX" mode is the smallest.
  • Figure 2 is a simulation diagram of the relationship between the idler light intensity and the zero dispersion wavelength of the optical fiber using the "XYYX" mode of FWM. As shown in Figure 2, the horizontal axis represents the zero dispersion wavelength of the optical fiber (in nm), and the vertical axis represents the idler light intensity (in dBm).
  • the idler light intensity is the highest when the zero dispersion wavelength of the optical fiber is 1300.09nm and 1304.58nm, but the polarization state of the idler light when the intensity is the highest is orthogonal to the polarization state of the service light of the corresponding channel, and the interference to the service light is very small. It can be seen that the "XYYX" mode is more helpful to reduce the interference of idler light on service light.
  • the TOSA provided in the embodiment of the present application is introduced in detail below. It should be noted that the number of light sources in the TOSA provided in the embodiment of the present application is greater than or equal to 4. For the sake of ease of introduction, this application mainly introduces 4 light sources and 8 light sources as examples. The embodiments with other numbers of light sources can be flexibly transformed on this basis. The specific transformation method can be known by those skilled in the art based on the introduction of this application. As an example, the TOSA provided in this application can be applied to a multi-channel ( ⁇ 4 channels) wavelength division multiplexing system in the O band with a wavelength interval less than 20nm, and the transmission distance is greater than 2km (including LR, ER, ZR, etc.).
  • FIG3 is a schematic diagram of the first structure of TOSA in an embodiment of the present application.
  • TOSA includes four light sources (light source 101, light source 102, light source 103 and light source 104), a polarization rotation unit 20 and a combining unit 30.
  • the four light sources are used to emit four light beams respectively, for example, light source 101 emits light beam 1, light source 102 emits light beam 2, light source 103 emits light beam 3, and light source 104 emits light beam 4.
  • the four light beams have the same initial polarization state and the wavelengths of the four light beams are different.
  • the four light beams are light beam 1, light beam 2, light beam 3 and light beam 4 in order from small to large wavelengths.
  • the wavelength bands of the four light beams may be different.
  • the central wavelength of light beam 1 is 1295nm
  • the central wavelength of light beam 2 is 1300nm
  • the central wavelength of light beam 3 is 1305nm
  • the central wavelength of light beam 4 is 1309nm.
  • the polarization rotation unit 20 is used to adjust the polarization state of at least two light beams so that the polarization state 1 of the light beam 1 and the light beam 4 is perpendicular to the polarization state 2 of the light beam 2 and the light beam 3.
  • the combining unit 30 is used to combine the four light beams output by the polarization rotation unit 20 to obtain a combined light beam. It should be understood that the present application does not limit the specific type of the combining unit 30. For example, the combining unit 30 can use a z-block combiner.
  • each light source includes a laser and a collimating lens
  • the collimating lens is used to collimate the divergent light beam emitted by the laser.
  • light source 101 includes a laser 101a and a collimating lens 101b
  • light source 102 includes a laser 102a and a collimating lens 102b
  • light source 103 includes a laser 103a and a collimating lens 103b
  • light source 104 includes a laser 104a and a collimating lens 104b.
  • FIG4(a) is a schematic diagram of the second structure of the TOSA in the embodiment of the present application.
  • the polarization rotation unit 20 includes a polarization rotation element 201 and a polarization rotation element 202.
  • the initial polarization state of the four light beams emitted by the four light sources is polarization state 1, and the polarization rotation element 201 is used to adjust the light beam 2 to polarization state 2, and the polarization rotation element 202 is used to adjust the light beam 3 to polarization state 2.
  • Light beam 1 and light beam 4 still maintain their initial polarization state, that is, polarization state 1.
  • FIG4(b) is a schematic diagram of the third structure of the TOSA in the embodiment of the present application.
  • the polarization rotation unit 20 includes Polarization rotation element 201 and polarization rotation element 202.
  • the initial polarization state of the four light beams emitted by the four light sources is polarization state 2.
  • Polarization rotation element 201 is used to adjust light beam 1 to polarization state 1
  • polarization rotation element 202 is used to adjust light beam 4 to polarization state 1.
  • Light beam 2 and light beam 3 still maintain their initial polarization state, that is, polarization state 2.
  • the present application does not limit the specific types of the polarization rotation element 201 and the polarization rotation element 202.
  • the polarization rotation element 201 and the polarization rotation element 202 may be half-wave plates.
  • the TOSA further includes a polarization-independent isolator 40.
  • the polarization-independent isolator 40 is used to transmit the combined light beam output by the combining unit 30 and to isolate the echo reflected light beam of the combined light beam. It should be understood that since the combined light beam output by the combining unit 20 includes two polarization states, polarization state 1 and polarization state 2, the polarization-independent isolator 40 is required.
  • FIG5 is a fourth structural schematic diagram of a TOSA in an embodiment of the present application.
  • the polarization rotation unit 20 includes a polarization rotation element 203, a polarization rotation element 204, a polarization rotation element 205, and a polarization rotation element 206.
  • the polarization rotation element 203 is used to adjust the light beam 1 from an initial polarization state to a polarization state 1
  • the polarization rotation element 204 is used to adjust the light beam 2 from an initial polarization state to a polarization state 2
  • the polarization rotation element 205 is used to adjust the light beam 3 from an initial polarization state to a polarization state 2
  • the polarization rotation element 206 is used to adjust the light beam 4 from an initial polarization state to a polarization state 1.
  • the polarization rotation element 203 and the polarization rotation element 206 use the same type of polarization-dependent isolator 1
  • the polarization rotation element 204 and the polarization rotation element 205 use the same type of polarization-dependent isolator 2.
  • the polarization-dependent isolator 1 can rotate the initial polarization state forward by 45° to obtain polarization state 1
  • the polarization-dependent isolator 2 can rotate the initial polarization state backward by 45° to obtain polarization state 2, so that polarization state 1 is perpendicular to polarization state 2.
  • the polarization rotation element 203 is also used to isolate the echo reflected beam of the light beam 1
  • the polarization rotation element 204 is also used to isolate the echo reflected beam of the light beam 2
  • the polarization rotation element 205 is also used to isolate the echo reflected beam of the light beam 3
  • the polarization rotation element 206 is also used to isolate the echo reflected beam of the light beam 4.
  • FIG6 is a fifth structural schematic diagram of a TOSA in an embodiment of the present application.
  • the TOSA includes four light sources (light source 101, light source 102, light source 103 and light source 104), a first combining unit 50, a polarization rotation unit 60 and a second combining unit 70.
  • the four light sources are used to emit four light beams respectively, for example, light source 101 emits light beam 1, light source 102 emits light beam 2, light source 103 emits light beam 3, and light source 104 emits light beam 4.
  • the four light beams have the same initial polarization state and the wavelengths of the four light beams are different.
  • the four light beams are light beam 1, light beam 2, light beam 3 and light beam 4 in order from small to large wavelength.
  • the first combining unit 50 is used to combine light beam 1 and light beam 4 to obtain a first combined light beam, and combine light beam 2 and light beam 3 to obtain a second combined light beam.
  • the polarization rotation unit 60 is used to adjust the polarization state of at least one of the first combined light beam and the second combined light beam, so that the polarization state 1 of the first combined light beam is perpendicular to the polarization state 2 of the second combined light beam.
  • the second combining unit 70 is used to combine the first combined light beam and the second combined light beam output by the polarization rotation unit 60 to obtain a third combined light beam. It should be understood that the present application does not limit the specific type of the second combining unit 70.
  • the second combining unit 70 can adopt a polarization beam combiner (PBC).
  • the polarization state 1 of the first combined light beam is perpendicular to the polarization state 2 of the second combined light beam after passing through the polarization rotation unit 60, and the first combined light beam includes light beam 1 and light beam 4, and the second combined light beam includes light beam 2 and light beam 3, the combined light beam finally output by the TOSA satisfies the above-mentioned polarization state form of "XYYX", wherein "X” corresponds to polarization state 1 and "Y” corresponds to polarization state 2, thereby effectively reducing the influence of FWM.
  • FIG7(a) is a sixth structural schematic diagram of the TOSA in the embodiment of the present application.
  • the polarization rotation unit 60 includes a polarization-dependent isolator 601 and a polarization rotation element 602.
  • the polarization-dependent isolator 601 is used to transmit the first combined light beam and the second combined light beam, and to isolate the echo reflected light beam of the first combined light beam and the echo reflected light beam of the second combined light beam.
  • the initial polarization state of the four light beams emitted by the four light sources is polarization state 1, and the polarization rotation element 602 is used to adjust the second combined light beam output by the polarization-dependent isolator 601 to polarization state 2.
  • the first combining unit 50 includes a reflective element 501, a first combining element 502, and a second combining element 503.
  • the reflective element 501 is used to reflect the light beam 1 and the light beam 2.
  • the first combining element 502 is used to combine the light beam 4 and the reflected light beam 1 to obtain a first combined light beam.
  • the second combining element 503 is used to combine the light beam 3 and the reflected light beam 2 to obtain a second combined light beam.
  • FIG7(b) is a seventh structural schematic diagram of the TOSA in the embodiment of the present application.
  • the polarization rotation unit 60 includes a polarization-dependent isolator 601 and a polarization rotation element 602.
  • the polarization-dependent isolator 601 is used to transmit the first combined light beam and the second combined light beam, and to isolate the echo reflected light beam of the first combined light beam and the echo reflected light beam of the second combined light beam.
  • the initial polarization state of the four light beams emitted by the four light sources is polarization state 2, and the polarization rotation element 602 is used to adjust the first combined light beam output by the polarization-dependent isolator 601 to polarization state 1.
  • the first combining unit 50 includes a reflective element 501, a first combining element 502, and a second combining element 503.
  • the reflective element 501 is used to reflect the light beam 3 and the light beam 4.
  • the first combining element 502 is used to combine the light beam 1 and the reflected light beam 4 to obtain a first combined light beam.
  • the second combining element 503 is used to combine the light beam 2 and the reflected light beam 3 to obtain a second combined light beam.
  • the present application does not limit the specific type of the polarization rotation element 602.
  • the polarization rotation element 602 may be a half-wave plate.
  • the first wave combining unit 50 in the TOSA shown in FIG7(a) may also adopt the structure of the first wave combining unit 50 in the TOSA shown in FIG7(b), and the first wave combining unit 50 in the TOSA shown in FIG7(b) may also adopt the structure of the first wave combining unit 50 in the TOSA shown in FIG7(a).
  • FIG8 is a schematic diagram of the eighth structure of the TOSA in the embodiment of the present application.
  • the polarization rotation unit 60 includes a polarization rotation element 603 and a polarization rotation element 604.
  • the polarization rotation element 603 is used to adjust the first combined light beam from the initial polarization state to polarization state 1
  • the polarization rotation element 604 is used to adjust the second combined light beam from the initial polarization state to polarization state 2.
  • the polarization rotation element 603 uses the polarization-dependent isolator 1, and the polarization rotation element 604 uses the polarization-dependent isolator 2.
  • the polarization-dependent isolator 1 can rotate the initial polarization state forward by 45° to obtain the polarization state 1
  • the polarization-dependent isolator 2 can rotate the initial polarization state backward by 45° to obtain the polarization state 2, so that the polarization state 1 is perpendicular to the polarization state 2.
  • the polarization rotation element 603 is also used to isolate the echo reflected beam of the first combined light beam
  • the polarization rotation element 604 is also used to isolate the echo reflected beam of the second combined light beam.
  • the first combining unit 50 includes a reflective element 501, a first combining element 502, and a second combining element 503.
  • the reflective element 501 is used to reflect the light beam 1 and the light beam 2.
  • the first combining element 502 is used to combine the light beam 4 and the reflected light beam 1 to obtain a first combined light beam.
  • the second combining element 503 is used to combine the light beam 3 and the reflected light beam 2 to obtain a second combined light beam.
  • the first combining unit 50 may also adopt the structure of the first combining unit 50 in the TOSA shown in FIG. 7( b ), and no drawings or text descriptions are provided here.
  • the TOSA including 8 light sources is obtained by simply expanding the TOSA structure including 4 light sources, which is equivalent to expanding the polarization state form of the TOSA output from "XYYX" to "XYYXXYYX".
  • TOSA structures including 8 light sources provided below, other transformations using technologies known in the art are also within the scope of protection of the present application and are not listed here one by one.
  • FIG9 is a ninth structural schematic diagram of a TOSA in an embodiment of the present application.
  • the TOSA includes eight light sources (light source 101, light source 102, light source 103, light source 104, light source 105, light source 106, light source 107, light source 108), four polarization rotation elements (polarization rotation element 207, polarization rotation element 208, polarization rotation element 209 and polarization rotation element 210), a combiner 30 and a polarization-independent isolator 40.
  • the eight light beams output by the eight light sources are, in order from small to large wavelength, light beam 1, light beam 2, light beam 3, light beam 4, light beam 5, light beam 6, light beam 7 and light beam 8, taking the initial polarization state of the eight light beams as polarization state 1 as an example.
  • the polarization rotation element 207 is used to adjust the light beam 2 to polarization state 2
  • the polarization rotation element 208 is used to adjust the light beam 3 to polarization state 2
  • the polarization rotation element 209 is used to adjust the light beam 6 to polarization state 2
  • the polarization rotation element 210 is used to adjust the light beam 7 to polarization state 2.
  • the combining unit 30 combines the eight light beams to obtain a combined light beam, and the polarization-independent isolator 40 is used to transmit the combined light beam output by the combining unit 30 and to isolate the echo reflected light beam of the combined light beam.
  • FIG10 is a schematic diagram of the tenth structure of TOSA in an embodiment of the present application.
  • TOSA includes eight light sources (light source 101, light source 102, light source 103, light source 104, light source 105, light source 106, light source 107, light source 108), six reflective elements (reflective element 1, reflective element 2, reflective element 3, reflective element 4, reflective element 5 and reflective element 6), six wave combining elements (wave combining element 7, wave combining element 8, wave combining element 9, wave combining element 10, wave combining element 11 and wave combining element 12), polarization-dependent isolator 601, polarization rotation element 602 and wave combining unit 70.
  • light sources light source 101, light source 102, light source 103, light source 104, light source 105, light source 106, light source 107, light source 108
  • six reflective elements reflective element 1, reflective element 2, reflective element 3, reflective element 4, reflective element 5 and reflective element 6
  • six wave combining elements wave combining element 7, wave combining element 8, wave combining element 9, wave combining element
  • the eight light beams output by the eight light sources are beam 1, beam 2, beam 3, beam 4, beam 5, beam 6, beam 7 and beam 8 in order from small to large wavelengths, taking the initial polarization state of the eight light beams as polarization state 1 as an example.
  • Reflective element 1 is used to reflect beam 1
  • wave combining element 7 is used to combine beam 1 and beam 4 to obtain combined beam 1.
  • Reflection element 2 is used to reflect light beam 2
  • combining element 8 is used to combine light beam 2 and light beam 3 to obtain combined light beam 2.
  • Reflection element 3 is used to reflect light beam 5, and combining element 9 is used to combine light beam 5 and light beam 8 to obtain combined light beam 3.
  • Reflection element 4 is used to reflect light beam 6, and combining element 10 is used to combine light beam 6 and light beam 7 to obtain combined light beam 4.
  • Reflection element 5 is used to reflect combined light beam 1
  • combining element 11 is used to combine combined light beam 1 and combined light beam 3 to obtain combined light beam 5.
  • Reflection element 6 is used to reflect combined light beam 2
  • combining element 12 is used to combine combined light beam 2 and combined light beam 4 to obtain combined light beam 6.
  • Polarization-dependent isolator 601 is used to transmit combined light beam 5 and combined light beam 6, and to isolate The echo reflected beam of the combined light beam 5 and the echo reflected beam of the combined light beam 6.
  • the polarization rotation element 602 is used to adjust the combined light beam 6 output by the polarization dependent isolator 601 to polarization state 2.
  • the combining unit 70 is used to combine the combined light beam 5 with polarization state 1 and the combined light beam 6 with polarization state 2 to obtain the combined light beam 7.
  • FIG11 is a schematic diagram of the eleventh structure of the TOSA in the embodiment of the present application.
  • the TOSA includes eight light sources (light source 101, light source 102, light source 103, light source 104, light source 105, light source 106, light source 107, light source 108), four polarization rotation elements (polarization rotation element 13, polarization rotation element 14, polarization rotation element 15 and polarization rotation element 16), four wave combining elements (wave combining element 17, wave combining element 18, wave combining element 19 and wave combining element 20), a wave combining unit 30 and a polarization-independent isolator 40.
  • light sources light source 101, light source 102, light source 103, light source 104, light source 105, light source 106, light source 107, light source 108
  • four polarization rotation elements polarization rotation element 13, polarization rotation element 14, polarization rotation element 15 and polarization rotation element 16
  • four wave combining elements wave combining element 17, wave combining element 18, wave combining element 19 and wave
  • the eight light beams output by the eight light sources are beam 1, beam 2, beam 3, beam 4, beam 5, beam 6, beam 7 and beam 8 in order from small to large wavelengths, taking the initial polarization states of the eight light beams as polarization state 2 as an example.
  • the polarization rotation element 13 is used to adjust the light beam 1 to polarization state 1
  • the wave combining element 17 is used to combine the light beam 1 with polarization state 1 and the light beam 2 with polarization state 2 to obtain the combined light beam 1.
  • the polarization rotation element 14 is used to adjust the light beam 4 to polarization state 1
  • the combining element 18 is used to combine the light beam 4 with polarization state 1 and the light beam 3 with polarization state 2 to obtain the combined light beam 2.
  • the polarization rotation element 15 is used to adjust the light beam 5 to polarization state 1, and the combining element 19 is used to combine the light beam 5 with polarization state 1 and the light beam 6 with polarization state 2 to obtain the combined light beam 3.
  • the polarization rotation element 16 is used to adjust the light beam 8 to polarization state 1, and the combining element 20 is used to combine the light beam 8 with polarization state 1 and the light beam 7 with polarization state 2 to obtain the combined light beam 4.
  • the combining unit 30 combines the combined light beam 1, the combined light beam 2, the combined light beam 3 and the combined light beam 4 to obtain the combined light beam 5, and the polarization-independent isolator 40 is used to transmit the combined light beam 5 output by the combining unit 30 and isolate the echo reflected light beam of the combined light beam 5.
  • the present application provides a solution for polarization interleaved transmission.
  • the polarization state of the output light beam of the combining unit is "XYYX", where "X" and "Y” represent two polarization states that are perpendicular to each other.
  • the polarization interleaved transmission method designed by the present application can effectively reduce the impact of FWM.
  • the polarization interleaved transmission scheme provided by the present application is more helpful in reducing the interference of idle light on business light.
  • the embodiment of the present application also provides a light transmission method.
  • the light transmission method is applied to the TOSA introduced in the embodiment shown in FIG3 above.
  • FIG12 is a schematic diagram of an embodiment of a light transmission method provided in the embodiment of the present application.
  • the light transmission method includes the following steps.
  • the four light beams have the same initial polarization state and different wavelengths, and the four light beams are respectively the first light beam, the second light beam, the third light beam and the fourth light beam in order from small to large wavelength.
  • the first polarization state of the first light beam and the fourth light beam is perpendicular to the second polarization state of the second light beam and the third light beam.
  • the specific implementation of the polarization rotation unit can refer to the relevant introduction of the embodiments shown in Figures 4(a), 4(b) and 5 above, and will not be repeated here.
  • the four light beams output by the polarization rotation unit are combined by a combining unit to obtain a combined light beam.
  • the embodiment of the present application also provides another light transmission method.
  • the light transmission method is applied to the TOSA introduced in the embodiment shown in the above-mentioned FIG6.
  • FIG13 is a schematic diagram of another light transmission method provided in the embodiment of the present application.
  • the light transmission method includes the following steps.
  • the four light beams have the same initial polarization state and different wavelengths, and the four light beams are respectively the first light beam, the second light beam, the third light beam and the fourth light beam in order from small to large wavelength.
  • first multiplexing unit can refer to the relevant introduction of the embodiments shown in the above-mentioned Figures 7(a), 7(b) and 8, and will not be repeated here.
  • the first polarization state of the first combined light beam is perpendicular to the second polarization state of the second combined light beam.
  • the specific implementation of the polarization rotation unit can refer to the relevant introduction of the embodiments shown in Figures 7(a), 7(b) and 8 above, and will not be repeated here.

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Abstract

一种TOSA、光模块、光网络设备和光发射方法，可以较为有效地降低FWM的影响。TOSA包括：四个光源（101,102,103,104）、偏振旋转单元（20,60）和合波单元（30）。四个光源（101,102,103,104）用于分别发射四路光束。其中，四路光束具有相同的初始偏振态且四路光束的波长各不相同，四路光束按照波长从小到大的顺序依次为第一光束、第二光束、第三光束和第四光束。偏振旋转单元（20,60）用于对至少两路光束进行偏振态调节，以使得第一光束和第四光束具有的第一偏振态与第二光束和第三光束具有的第二偏振态垂直。合波单元（30）用于对偏振旋转单元（20,60）输出的四路光束进行合波得到合波光束。

Description

一种TOSA、光模块、光网络设备和光发射方法
本申请要求于2022年10月11日提交国家知识产权局、申请号为202211244258.7、发明名称为“一种TOSA、光模块、光网络设备和光发射方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及通信领域，尤其涉及一种TOSA、光模块、光网络设备和光发射方法。
背景技术
随着数据中心业务的发展，对于光模块的传输带宽的距离要求也越来越高，当前800G(单波200Gbps)强度调制/直接检测(Intensity Modulation/Direct Detection，IM/DD)模块是研究的重点，800G 2km的多源协议(Multi-Source Agreement，MSA)已经发布，继续演进到10km时，考虑到色散的影响，需要使用局域网-波分复用(Local Area Network-Wavelength Division Multiplexing，LAN-WDM)，随着传输距离的增大和波长间隔的减小，必须考虑四波混频(Four Wave Mixing,FWM)的影响。
FWM是光纤的一种非线性现象，当同时有两个以上的波长在一根光纤中传输时，FWM效应会产生一个新的波长，称之为闲频光，若闲频光落在业务光的带内，则会引入额外的噪声，现有技术没有提供能够降低FWM影响的最为有效的方案。
发明内容
本申请实施例提供了一种TOSA、光模块、光网络设备和光发射方法，可以较为有效地降低FWM的影响。
第一方面，本申请实施例提供了一种光发射模块(Transmitting Optical sub-assembly，TOSA)。该TOSA包括：四个光源、偏振旋转单元和合波单元。四个光源用于分别发射四路光束。其中，四路光束具有相同的初始偏振态且四路光束的波长各不相同，四路光束按照波长从小到下的顺序依次为第一光束、第二光束、第三光束和第四光束。偏振旋转单元用于对至少两路光束进行偏振态调节，以使得第一光束和第四光束具有的第一偏振态与第二光束和第三光束具有的第二偏振态垂直。合波单元用于对偏振旋转单元输出的四路光束进行合波得到合波光束。
在该实施方式中，提供了一种偏振间插发射的方案，以四路光束的初始偏振态是“XXXX”为例，合波单元输出光束的偏振态是“XYYX”，其中，“X”和“Y”表示相互垂直的两种偏振态。通过本申请设计的偏振间插发射方式，可以较为有效地降低FWM的影响。
在一些可能的实施方式中，四路光束的初始偏振态为第一偏振态，偏振旋转单元用于将第二光束和第三光束调节为第二偏振态。或者，四路光束的初始偏振态为第二偏振态，偏振旋转单元用于将第一光束和第四光束调节为第一偏振态。
在一些可能的实施方式中，偏振旋转单元包括第一偏振旋转元件和第二偏振旋转元件。若述四路光束的初始偏振态为第一偏振态，第一偏振旋转元件用于将第二光束调节为第二偏振态，第二偏振旋转元件用于将第三光束调节为第二偏振态。若述四路光束的初始偏振态为第二偏振态，第一偏振旋转元件用于将第一光束调节为第一偏振态，第二偏振旋转元件用于将第四光束调节为第一偏振态。
在一些可能的实施方式中，TOSA还包括偏振不相关隔离器，偏振不相关隔离器用于透传合波光束并隔离合波光束的回波反射光束。
在一些可能的实施方式中，偏振旋转单元用于将第一光束和第四光束由初始偏振态调节为第一偏振态，并将第二光束和第三光束由初始偏振态调节为第二偏振态。
在一些可能的实施方式中，偏振旋转单元包括两个第一偏振旋转元件和两个第二偏振旋转元件。两个第一偏振旋转单元用于分别将第一光束和第四光束由初始偏振态调节为第一偏振态；两个第二偏振旋转元件用于分别将第二光束和第三光束由初始偏振态调节为第二偏振态。
在一些可能的实施方式中，两个第一偏振旋转单元为第一偏振相关隔离器，两个第二偏振旋转单元为第二偏振相关隔离器。两个第一偏振旋转单元还用于分别隔离第一光束的回波反射光束和第四光束的回波反射光束。两个第二偏振旋转单元还用于分别隔离第二光束的回波反射光束和第三光束的回波反射光束。
在一些可能的实施方式中，合波单元为z-block合波器。
在一些可能的实施方式中，每个光源包括激光器和准直透镜，准直透镜用于对激光器发射的光束进行准直。
第二方面，本申请实施例提供了一种TOSA。该TOSA包括：四个光源、第一合波单元、偏振旋转单元和第二合波单元。四个光源用于分别发射四路光束。其中，四路光束具有相同的初始偏振态且四路光束的波长各不相同，四路光束按照波长从小到下的顺序依次为第一光束、第二光束、第三光束和第四光束。第一合波单元用于对第一光束和第四光束进行合波得到第一合波光束，并对第二光束和第三光束进行合波得到第二合波光束。偏振旋转单元用于对第一合波光束和第二合波光束中的至少一个合波光束进行偏振态调节，以使得第一合波光束具有的第一偏振态与第二合波光束具有的第二偏振态垂直。第二合波单元用于对偏振旋转单元输出的第一合波光束和第二合波光束进行合波得到第三合波光束。
在该实施方式中，提供了一种偏振间插发射的方案，以四路光束的初始偏振态是“XXXX”为例，合波单元输出光束的偏振态是“XYYX”，其中，“X”和“Y”表示相互垂直的两种偏振态。通过本申请设计的偏振间插发射方式，可以较为有效地降低FWM的影响。
在一些可能的实施方式中，偏振旋转单元包括偏振旋转元件和偏振相关隔离器。偏振相关隔离器用于透传第一合波光束和第二合波光束，并隔离第一合波光束的回波反射光束和第二合波光束的回波反射光束。若四路光束的初始偏振态为第一偏振态，偏振旋转元件用于将偏振相关隔离器输出的第二合波光束调节为第二偏振态。若四路光束的初始偏振态为第二偏振态，偏振旋转元件用于将偏振相关隔离器输出的第一合波光束调节为第一偏振态。
在一些可能的实施方式中，偏振旋转单元包括第一偏振旋转元件和第二偏振旋转元件。第一偏振旋转元件用于将第一合波光束由初始偏振态调节为第一偏振态。第二偏振旋转元件用于将第二合波光束由初始偏振态调节为第二偏振态。
在一些可能的实施方式中，第一偏振旋转元件为第一偏振相关隔离器，第二偏振旋转元件为第二偏振相关隔离器。第一偏振旋转元件还用于隔离第一合波光束的回波反射光束。第二偏振旋转元件还用于隔离第二合波光束的回波反射光束。
在一些可能的实施方式中，第一合波单元包括反射元件、第一合波元件和第二合波元件。反射元件用于对第一光束和第二光束进行反射。第一合波元件用于对经过反射的第一光束和第四光束进行合波得到第一合波光束。第二合波元件用于对经过反射的第二光束和第三光束进行合波得到第二合波光束。或者，反射元件用于对第三光束和第四光束进行反射。第一合波元件用于对第一光束和经过反射的第四光束进行合波得到第一合波光束。第二合波元件用于对第二光束和经过反射的第三光束进行合波得到第二合波光束。
在一些可能的实施方式中，第二合波单元为偏振合波器(polarization beam combiner，PBC)。
在一些可能的实施方式中，每个光源包括激光器和准直透镜，准直透镜用于对激光器发射的光束进行准直。
第三方面，本申请实施例提供了一种光模块。该光模块包括如上述第一方面和第二方面任一实施方式介绍的TOSA、光接收模块(Receiving Optical sub-assembly，ROSA)和光纤连接端口。TOSA用于向光纤连接端口输出光束。ROSA用于接收来自光纤连接端口的光束。
第四方面，本申请实施例提供了一种光网络设备。该光网络设备包括上述第三方面介绍的光模块，光模块集成在光网络设备中。
第五方面，本申请实施例提供了一种光发射方法，光发射方法应用于光发射模块TOSA，TOSA包括：四个光源、偏振旋转单元和合波单元。方法包括：通过四个光源分别发射四路光束。四路光束具有相同的初始偏振态且四路光束的波长各不相同，四路光束按照波长从小到下的顺序依次为第一光束、第二光束、第三光束和第四光束。通过偏振旋转单元对至少两路光束进行偏振态调节，以使得第一光束和第四 光束具有的第一偏振态与第二光束和第三光束具有的第二偏振态垂直。通过合波单元对偏振旋转单元输出的四路光束进行合波得到合波光束。
在一些可能的实施方式中，四路光束的初始偏振态为第一偏振态，通过偏振旋转单元对至少两路光束进行偏振态调节包括：通过偏振旋转单元将第二光束和第三光束调节为第二偏振态。或者，四路光束的初始偏振态为第二偏振态，通过偏振旋转单元对至少两路光束进行偏振态调节包括：通过偏振旋转单元将第一光束和第四光束调节为第一偏振态。
在一些可能的实施方式中，偏振旋转单元包括第一偏振旋转元件和第二偏振旋转元件，通过偏振旋转单元对至少两路光束进行偏振态调节包括：若述四路光束的初始偏振态为第一偏振态，通过第一偏振旋转元件将第二光束调节为第二偏振态，通过第二偏振旋转元件将第三光束调节为第二偏振态。若述四路光束的初始偏振态为第二偏振态，通过第一偏振旋转元件将第一光束调节为第一偏振态，通过第二偏振旋转元件将第四光束调节为第一偏振态。
在一些可能的实施方式中，TOSA还包括偏振不相关隔离器，方法还包括：通过偏振不相关隔离器透传合波光束并隔离合波光束的回波反射光束。
在一些可能的实施方式中，通过偏振旋转单元对至少两路光束进行偏振态调节包括：通过偏振旋转单元将第一光束和第四光束由初始偏振态调节为第一偏振态，并将第二光束和第三光束由初始偏振态调节为第二偏振态。
在一些可能的实施方式中，偏振旋转单元包括两个第一偏振旋转元件和两个第二偏振旋转元件，通过偏振旋转单元对至少两路光束进行偏振态调节包括：通过两个第一偏振旋转单元分别将第一光束和第四光束由初始偏振态调节为第一偏振态。通过两个第二偏振旋转元件分别将第二光束和第三光束由初始偏振态调节为第二偏振态。
在一些可能的实施方式中，两个第一偏振旋转单元为第一偏振相关隔离器，两个第二偏振旋转单元为第二偏振相关隔离器，方法还包括：通过两个第一偏振旋转单元还分别隔离第一光束的回波反射光束和第四光束的回波反射光束。通过两个第二偏振旋转单元还分别隔离第二光束的回波反射光束和第三光束的回波反射光束。
第六方面，本申请实施例提供了一种光发射方法，光发射方法应用于光发射模块TOSA，TOSA包括：四个光源、第一合波单元、偏振旋转单元和第二合波单元。方法包括：通过四个光源分别发射四路光束。四路光束具有相同的初始偏振态且四路光束的波长各不相同，四路光束按照波长从小到下的顺序依次为第一光束、第二光束、第三光束和第四光束。通过第一合波单元对第一光束和第四光束进行合波得到第一合波光束，并对第二光束和第三光束进行合波得到第二合波光束。通过偏振旋转单元对第一合波光束和第二合波光束中的至少一个合波光束进行偏振态调节，以使得第一合波光束具有的第一偏振态与第二合波光束具有的第二偏振态垂直。通过第二合波单元对偏振旋转单元输出的第一合波光束和第二合波光束进行合波得到第三合波光束。
在一些可能的实施方式中，偏振旋转单元包括偏振旋转元件和偏振相关隔离器，通过偏振旋转单元对第一合波光束和第二合波光束中的至少一个合波光束进行偏振态调节包括：通过偏振相关隔离器透传第一合波光束和第二合波光束，并隔离第一合波光束的回波反射光束和第二合波光束的回波反射光束。若四路光束的初始偏振态为第一偏振态，通过偏振旋转元件将偏振相关隔离器输出的第二合波光束调节为第二偏振态。若四路光束的初始偏振态为第二偏振态，通过偏振旋转元件将偏振相关隔离器输出的第一合波光束调节为第一偏振态。
在一些可能的实施方式中，偏振旋转单元包括第一偏振旋转元件和第二偏振旋转元件，通过偏振旋转单元对第一合波光束和第二合波光束中的至少一个合波光束进行偏振态调节包括：通过第一偏振旋转元件将第一合波光束由初始偏振态调节为第一偏振态。通过第二偏振旋转元件将第二合波光束由初始偏振态调节为第二偏振态。
在一些可能的实施方式中，第一偏振旋转元件为第一偏振相关隔离器，第二偏振旋转元件为第二偏振相关隔离器，方法还包括：通过第一偏振旋转元件隔离第一合波光束的回波反射光束。通过第二偏振旋转元件隔离第二合波光束的回波反射光束。
在一些可能的实施方式中，第一合波单元包括反射元件、第一合波元件和第二合波元件，通过第一 合波单元对第一光束和第四光束进行合波得到第一合波光束，并对第二光束和第三光束进行合波得到第二合波光束包括：通过反射元件对第一光束和第二光束进行反射；通过第一合波元件对经过反射的第一光束和第四光束进行合波得到第一合波光束；通过第二合波元件对经过反射的第二光束和第三光束进行合波得到第二合波光束。或者，通过反射元件对第三光束和第四光束进行反射；通过第一合波元件对第一光束和经过反射的第四光束进行合波得到第一合波光束；通过第二合波元件对第二光束和经过反射的第三光束进行合波得到第二合波光束。
本申请实施例中，TOSA中四个光源输出具有相同初始偏振态且波长各不相同的四路光束。偏振旋转单元对其中至少两路光束进行偏振态调节，使得其中第一光束和第四光束具有的第一偏振态与第二光束和第三光束具有的第二偏振态垂直。进而，合波单元对偏振旋转单元输出的四路光束进行合波并输出合波光束。应理解，本申请提供了一种偏振间插发射的方案，以四路光束的初始偏振态是“XXXX”为例，合波单元输出光束的偏振态是“XYYX”，其中，“X”和“Y”表示相互垂直的两种偏振态。通过本申请设计的偏振间插发射方式，可以较为有效地降低FWM的影响。并且，采用本申请提供的偏振间插发射方案更有助于减小闲频光对业务光的干扰。
附图说明
图1为采用不同光发射模式的FWM代价的仿真对比示意图；
图2为采用“XYYX”模式下FWM的闲频光强度与光纤零色散波长的关系仿真示意图；
图3为本申请实施例中TOSA的第一种结构示意图；
图4(a)为本申请实施例中TOSA的第二种结构示意图；
图4(b)为本申请实施例中TOSA的第三种结构示意图；
图5为本申请实施例中TOSA的第四种结构示意图；
图6为本申请实施例中TOSA的第五种结构示意图；
图7(a)为本申请实施例中TOSA的第六种结构示意图；
图7(b)为本申请实施例中TOSA的第七种结构示意图；
图8为本申请实施例中TOSA的第八种结构示意图；
图9为本申请实施例中TOSA的第九种结构示意图；
图10为本申请实施例中TOSA的第十种结构示意图；
图11为本申请实施例中TOSA的第十一种结构示意图；
图12为本申请实施例提供的一种光发射方法的实施例示意图；
图13为本申请实施例提供的另一种光发射方法的实施例示意图。
具体实施方式
本申请实施例提供了一种TOSA、光模块、光网络设备和光发射方法，可以较为有效地降低FWM的影响。需要说明的是，本申请的说明书和权利要求书及上述附图中的术语“第一”、“第二”、“第三”、“第四”等(如果存在)是用于区别类似的对象，而不必用于描述特定的顺序或先后次序。应该理解这样使用的数据在适当情况下可以互换，以便这里描述的实施例能够以除了在这里图示或描述的内容以外的顺序实施。此外，术语“包括”和“具有”以及他们的任何变形，意图在于覆盖不排他的包含，例如，包含了一系列步骤或单元的过程、方法、系统、产品或设备不必限于清楚地列出的那些步骤或单元，而是可包括没有清楚地列出的或对于这些过程、方法、产品或设备固有的其它步骤或单元。
本申请实施例可主要应用于光通信场景，例如数据中心光互连的光网络。作为光网络中的关键构成，光模块担负着将网络信号进行光电转换及传输的任务，是整个网络能够正常通信的基础。需要说明的是，光模块包括光发射模块(Transmitting Optical sub-assembly，TOSA)和光接收模块(Receiving Optical sub-assembly，ROSA)。TOSA用于将电信号转换为光信号，并将光信号传输至光纤。ROSA用于接收来自光纤的光信号，并将光信号转换为电信号。
在一些可能的场景中，TOSA会采用波分复用(wavelength division multiplexing，WDM)技术将两种或多种不同波长的光载波信号经复用器(亦称合波器)汇合在一起得到合波信号。ROSA接收到的合 波信号经过解复用器(亦称分波器或称去复用器)将各种波长的光载波分离，然后进一步处理以恢复原信号。应理解，当同时有两个以上的波长在一根光纤中传输时，四波混频(Four Wave Mixing,FWM)效应会产生一个新的波长，称之为闲频光，若闲频光落在业务光的带内，则会引入额外的噪声。
为此，本申请实施例提供了一种TOSA，可以实现偏振间插发射，有助于降低FWM的影响。以输出四路光束为例，四个光源分别发射的四路光束都具有相同的原始偏振态，四路原始偏振态的光束记为“XXXX”，TOSA经过处理使得最终向光纤输出的四路光束的偏振态记为“XYYX”。其中，“X”和“Y”表示相互垂直的两种偏振态。应理解，“XYYX”这种偏振间插的方式相较于“XXXX”可以降低FWM影响，并且“XYYX”相较于“XYXY”等其他偏振间插的方式是更为有效的降低FWM影响的方案。
图1为采用不同光发射模式的FWM代价的仿真对比示意图。如图1所示，横坐标表示入纤光功率(单位dBm)，纵坐标表示FWM代价(单位dB)，其中，FWM代价可以理解为由于FWM影响引入的噪声大小。从图1中可以看出，当FWM代价为1dB时，“XXXX”模式对应的入纤光功率约为1dBm，“XYXY”模式对应的入纤光功率约为5dBm，“XYYX”模式对应的入纤光功率约为11dBm。也就是说，当FWM代价一致时，采用“XYYX”模式的入纤光功率最高，效果最好。换言之，当入纤光功率一致时，采用“XYYX”模式的FWM代价最小。
图2为采用“XYYX”模式下FWM的闲频光强度与光纤零色散波长的关系仿真示意图。如图2所示，横坐标表示光纤零色散波长(单位nm)，纵坐标表示闲频光强度(单位dBm)。以四路光束的工作波长分别是1295.56nm、1300.09nm、1304.58nm和1309.14nm为例，光纤零色散波长为1300.09nm和1304.58nm时产生的闲频光强度最高，但闲频光强度最高时的偏振态与对应信道的业务光的偏振态正交，对业务光的干扰很小。由此可以看出，采用“XYYX”模式更有助于减小闲频光对业务光的干扰。
下面对本申请实施例提供的TOSA进行详细介绍。需要说明的是，本申请实施例提供的TOSA中光源的数量大于或等于4，为了便于介绍，本申请主要以4个光源和8个光源为例进行介绍，其他光源数量的实施例可以在此基础上进行灵活变换，具体的变换方式本领域技术人员可以基于本申请的介绍获知。作为一个示例，本申请提供的TOSA可应用于O波段且波长间隔小于20nm的多路(≥4路)波分复用系统中，传输距离大于2km(包括LR、ER、ZR等)。
图3为本申请实施例中TOSA的第一种结构示意图。如图3所示，TOSA包括四个光源(光源101、光源102、光源103和光源104)、偏振旋转单元20和合波单元30。具体地，四个光源用于分别发射四路光束，例如，光源101发射光束1，光源102发射光束2，光源103发射光束3，光源104发射光束4。其中，四路光束具有相同的初始偏振态且四路光束的波长各不相同，四路光束按照波长从小到大的顺序依次为光束1、光束2、光束3和光束4。应理解，在一些可能的实施方式中，具体可以是四路光束的波段各不相同，例如，光束1的中心波长为1295nm，光束2的中心波长为1300nm，光束3的中心波长为1305nm，光束4的中心波长为1309nm。偏振旋转单元20用于对至少两路光束进行偏振态调节，以使得光束1和光束4具有的偏振态1与光束2和光束3具有的偏振态2垂直。应理解，在实际应用中，如果偏振态1与偏振态2不完全垂直，但是只要在一定的误差范围内，本申请也可视为偏振态1与偏振态2垂直。合波单元30用于对偏振旋转单元20输出的四路光束进行合波得到合波光束。应理解，本申请不限定合波单元30的具体类型，例如，合波单元30可以采用z-block合波器。
需要说明的是，由于经过偏振旋转单元20后光束1和光束4具有的偏振态1与光束2和光束3具有的偏振态2垂直，因此TOSA最终输出的合波光束满足上述的“XYYX”的偏振态形式，其中，“X”对应偏振态1，“Y”对应偏振态2，有效降低了FWM的影响。
在一些可能的实施方式中，每个光源包括激光器和准直透镜，准直透镜用于对激光器发射的发散光束进行准直。例如，光源101包括激光器101a和准直透镜101b，光源102包括激光器102a和准直透镜102b，光源103包括激光器103a和准直透镜103b，光源104包括激光器104a和准直透镜104b。
图4(a)为本申请实施例中TOSA的第二种结构示意图。如图4(a)所示，偏振旋转单元20包括偏振旋转元件201和偏振旋转元件202。四个光源发射的四路光束的初始偏振态为偏振态1，偏振旋转元件201用于将光束2调节为偏振态2，偏振旋转元件202用于将光束3调节为偏振态2。光束1和光束4仍保持其初始偏振态，即偏振态1。
图4(b)为本申请实施例中TOSA的第三种结构示意图。如图4(b)所示，偏振旋转单元20包括 偏振旋转元件201和偏振旋转元件202。四个光源发射的四路光束的初始偏振态为偏振态2，偏振旋转元件201用于将光束1调节为偏振态1，偏振旋转元件202用于将光束4调节为偏振态1。光束2和光束3仍保持其初始偏振态，即偏振态2。
需要说明的是，本申请不限定偏振旋转元件201和偏振旋转元件202的具体类型，例如，偏振旋转元件201和偏振旋转元件202可以采用半波片。
在一些可能的实施方式中，如图4(a)和图4(b)所示，TOSA还包括偏振不相关隔离器40。偏振不相关隔离器40用于透传合波单元30输出的合波光束并隔离合波光束的回波反射光束。应理解，由于合波单元20输出的合波光束中包括偏振态1和偏振态2两种偏振态，因此需要采用偏振不相关隔离器40。
图5为本申请实施例中TOSA的第四种结构示意图。如图5所示，偏振旋转单元20包括偏振旋转元件203、偏振旋转元件204、偏振旋转元件205和偏振旋转元件206。偏振旋转元件203用于将光束1由初始偏振态调节为偏振态1，偏振旋转元件204用于将光束2由初始偏振态调节为偏振态2，偏振旋转元件205用于将光束3由初始偏振态调节为偏振态2，偏振旋转元件206用于将光束4由初始偏振态调节为偏振态1。
在一种可能的实施方式中，偏振旋转元件203和偏振旋转元件206采用相同类型的偏振相关隔离器1，偏振旋转元件204和偏振旋转元件205采用相同类型的偏振相关隔离器2。例如，偏振相关隔离器1可以将初始偏振态正向旋转45°得到偏振态1，偏振相关隔离器2可以将初始偏振态反向旋转45°得到偏振态2，从而使得偏振态1与偏振态2垂直。需要说明的是，偏振旋转元件203还用于隔离光束1的回波反射光束，偏振旋转元件204还用于隔离光束2的回波反射光束，偏振旋转元件205还用于隔离光束3的回波反射光束，偏振旋转元件206还用于隔离光束4的回波反射光束。
图6为本申请实施例中TOSA的第五种结构示意图。如图6所示，TOSA包括四个光源(光源101、光源102、光源103和光源104)、第一合波单元50、偏振旋转单元60和第二合波单元70。具体地，四个光源用于分别发射四路光束，例如，光源101发射光束1，光源102发射光束2，光源103发射光束3，光源104发射光束4。其中，四路光束具有相同的初始偏振态且四路光束的波长各不相同，四路光束按照波长从小到大的顺序依次为光束1、光束2、光束3和光束4。第一合波单元50用于对光束1和光束4进行合波得到第一合波光束，并对光束2和光束3进行合波得到第二合波光束。偏振旋转单元60用于对第一合波光束和第二合波光束中的至少一个合波光束进行偏振态调节，以使得第一合波光束具有的偏振态1与第二合波光束具有的偏振态2垂直。第二合波单元70用于对偏振旋转单元60输出的第一合波光束和第二合波光束进行合波得到第三合波光束。应理解，本申请不限定第二合波单元70的具体类型，例如，第二合波单元70可以采用偏振合波器(polarization beam combiner，PBC)。
需要说明的是，由于经过偏振旋转单元60后第一合波光束具有的偏振态1与第二合波光束具有的偏振态2垂直，且第一合波光束包括光束1和光束4，第二合波光束包括光束2和光束3，因此TOSA最终输出的合波光束满足上述的“XYYX”的偏振态形式，其中，“X”对应偏振态1，“Y”对应偏振态2，有效降低了FWM的影响。
图7(a)为本申请实施例中TOSA的第六种结构示意图。如图7(a)所示，偏振旋转单元60包括偏振相关隔离器601和偏振旋转元件602。偏振相关隔离器601用于透传第一合波光束和第二合波光束，并隔离第一合波光束的回波反射光束和第二合波光束的回波反射光束。四个光源发射的四路光束的初始偏振态为偏振态1，偏振旋转元件602用于将偏振相关隔离器601输出的第二合波光束调节为偏振态2。
在一种可能的实施方式中，第一合波单元50包括反射元件501、第一合波元件502和第二合波元件503。反射元件501用于对光束1和光束2进行反射。第一合波元件502用于对光束4和经过反射的光束1进行合波得到第一合波光束。第二合波元件503用于对光束3和经过反射的光束2进行合波得到第二合波光束。
图7(b)为本申请实施例中TOSA的第七种结构示意图。如图7(b)所示，偏振旋转单元60包括偏振相关隔离器601和偏振旋转元件602。偏振相关隔离器601用于透传第一合波光束和第二合波光束，并隔离第一合波光束的回波反射光束和第二合波光束的回波反射光束。四个光源发射的四路光束的初始偏振态为偏振态2，偏振旋转元件602用于将偏振相关隔离器601输出的第一合波光束调节为偏振态1。
在一种可能的实施方式中，第一合波单元50包括反射元件501、第一合波元件502和第二合波元件503。反射元件501用于对光束3和光束4进行反射。第一合波元件502用于对光束1和经过反射的光束4进行合波得到第一合波光束。第二合波元件503用于对光束2和经过反射的光束3进行合波得到第二合波光束。
需要说明的是，本申请不限定偏振旋转元件602的具体类型，例如，偏振旋转元件602可以采用半波片。还需要说明的是，上述7(a)所示的TOSA中第一合波单元50也可以采用图7(b)所示的TOSA中第一合波单元50的结构，上述图7(b)所示的TOSA中第一合波单元50也可以采用图7(a)所示的TOSA中第一合波单元50的结构。
图8为本申请实施例中TOSA的第八种结构示意图。如图8所示，偏振旋转单元60包括偏振旋转元件603和偏振旋转元件604。偏振旋转元件603用于将第一合波光束由初始偏振态调节为偏振态1，偏振旋转元件604用于将第二合波光束由初始偏振态调节为偏振态2。
在一种可能的实施方式中，偏振旋转元件603采用偏振相关隔离器1，偏振旋转元件604采用偏振相关隔离器2。例如，偏振相关隔离器1可以将初始偏振态正向旋转45°得到偏振态1，偏振相关隔离器2可以将初始偏振态反向旋转45°得到偏振态2，从而使得偏振态1与偏振态2垂直。需要说明的是，偏振旋转元件603还用于隔离第一合波光束的回波反射光束，偏振旋转元件604还用于隔离第二合波光束的回波反射光束。
在一种可能的实施方式中，第一合波单元50包括反射元件501、第一合波元件502和第二合波元件503。反射元件501用于对光束1和光束2进行反射。第一合波元件502用于对光束4和经过反射的光束1进行合波得到第一合波光束。第二合波元件503用于对光束3和经过反射的光束2进行合波得到第二合波光束。在另一种可能的实施方式中，第一合波单元50也可以采用图7(b)所示的TOSA中第一合波单元50的结构，此处不再提供附图展示和文字介绍。
下面对本申请实施例中包括8个光源的TOSA进行介绍，应理解，包括8个光源的TOSA是在上述包括4个光源的TOSA结构基础上进行简单扩展得到的，相当于将TOSA输出的偏振态形式由“XYYX”扩展为“XYYXXYYX”。除了下面提供的几种包括8个光源的TOSA结构之外，其他采用本领域公知技术进行的变换也在本申请的保护范围内，此处不再一一列举。
图9为本申请实施例中TOSA的第九种结构示意图。如图9所示，TOSA包括八个光源(光源101、光源102、光源103、光源104、光源105、光源106、光源107、光源108)、四个偏振旋转元件(偏振旋转元件207、偏振旋转元件208、偏振旋转元件209和偏振旋转元件210)、合波单元30和偏振不相关隔离器40。八个光源输出的八路光束按照波长从小到大的顺序依次为光束1、光束2、光束3、光束4、光束5、光束6、光束7和光束8，以八路光束的初始偏振态都为偏振态1为例。偏振旋转元件207用于将光束2调节为偏振态2，偏振旋转元件208用于将光束3调节为偏振态2，偏振旋转元件209用于将光束6调节为偏振态2，偏振旋转元件210用于将光束7调节为偏振态2。之后，合波单元30对八路光束进行合波得到合波光束，偏振不相关隔离器40用于透传合波单元30输出的合波光束并隔离合波光束的回波反射光束。
图10为本申请实施例中TOSA的第十种结构示意图。如图10所示，TOSA包括八个光源(光源101、光源102、光源103、光源104、光源105、光源106、光源107、光源108)、六个反射元件(反射元件1、反射元件2、反射元件3、反射元件4、反射元件5和反射元件6)、六个合波元件(合波元件7、合波元件8、合波元件9、合波元件10、合波元件11和合波元件12)、偏振相关隔离器601、偏振旋转元件602和合波单元70。八个光源输出的八路光束按照波长从小到大的顺序依次为光束1、光束2、光束3、光束4、光束5、光束6、光束7和光束8，以八路光束的初始偏振态都为偏振态1为例。反射元件1用反射光束1，合波元件7用于对光束1和光束4进行合波得到合波光束1。反射元件2用反射光束2，合波元件8用于对光束2和光束3进行合波得到合波光束2。反射元件3用反射光束5，合波元件9用于对光束5和光束8进行合波得到合波光束3。反射元件4用反射光束6，合波元件10用于对光束6和光束7进行合波得到合波光束4。反射元件5用于反射合波光束1，合波元件11用于对合波光束1和合波光束3进行合波得到合波光束5。反射元件6用于反射合波光束2，合波元件12用于对合波光束2和合波光束4进行合波得到合波光束6。偏振相关隔离器601用于透传合波光束5和合波光束6，并隔离 合波光束5的回波反射光束和合波光束6的回波反射光束。偏振旋转元件602用于将偏振相关隔离器601输出的合波光束6调节为偏振态2。合波单元70用于具有偏振态1的合波光束5和具有偏振态2的合波光束6进行合波得到合波光束7。
图11为本申请实施例中TOSA的第十一种结构示意图。如图11所示，TOSA包括八个光源(光源101、光源102、光源103、光源104、光源105、光源106、光源107、光源108)、四个偏振旋转元件(偏振旋转元件13、偏振旋转元件14、偏振旋转元件15和偏振旋转元件16)、四个合波元件(合波元件17、合波元件18、合波元件19和合波元件20)、合波单元30和偏振不相关隔离器40。八个光源输出的八路光束按照波长从小到大的顺序依次为光束1、光束2、光束3、光束4、光束5、光束6、光束7和光束8，以八路光束的初始偏振态都为偏振态2为例。偏振旋转元件13用于将光束1调节为偏振态1，合波元件17用于对具有偏振态1的光束1和具有偏振态2的光束2进行合波得到合波光束1。偏振旋转元件14用于将光束4调节为偏振态1，合波元件18用于对具有偏振态1的光束4和具有偏振态2的光束3进行合波得到合波光束2。偏振旋转元件15用于将光束5调节为偏振态1，合波元件19用于对具有偏振态1的光束5和具有偏振态2的光束6进行合波得到合波光束3。偏振旋转元件16用于将光束8调节为偏振态1，合波元件20用于对具有偏振态1的光束8和具有偏振态2的光束7进行合波得到合波光束4。之后，合波单元30对合波光束1、合波光束2、合波光束3和合波光束4进行合波得到合波光束5，偏振不相关隔离器40用于透传合波单元30输出的合波光束5并隔离合波光束5的回波反射光束。
通过上面的介绍可知，本申请提供了一种偏振间插发射的方案，以四路光束的初始偏振态是“XXXX”为例，合波单元输出光束的偏振态是“XYYX”，其中，“X”和“Y”表示相互垂直的两种偏振态。通过本申请设计的偏振间插发射方式，可以较为有效地降低FWM的影响。并且，采用本申请提供的偏振间插发射方案更有助于减小闲频光对业务光的干扰。
本申请实施例还提供了一种光发射方法。该光发射方法应用于上述图3所示实施例介绍的TOSA。图12为本申请实施例提供的一种光发射方法的实施例示意图。在该示例中，光发射方法包括如下步骤。
1201、通过四个光源分别发射四路光束。
应理解，四路光束具有相同的初始偏振态且四路光束的波长各不相同，四路光束按照波长从小到大的顺序依次为第一光束、第二光束、第三光束和第四光束。
1202、通过偏振旋转单元对至少两路光束进行偏振态调节。
应理解，经过偏振旋转单元后第一光束和第四光束具有的第一偏振态与第二光束和第三光束具有的第二偏振态垂直。需要说明的是，偏振旋转单元的具体实现方式可以参照上述图4(a)、图4(b)和图5所示实施例的相关介绍，此处不再赘述。
1203、通过合波单元对偏振旋转单元输出的四路光束进行合波得到合波光束。
本申请实施例还提供了另一种光发射方法。该光发射方法应用于上述图6所示实施例介绍的TOSA。图13为本申请实施例提供的另一种光发射方法的实施例示意图。在该示例中，光发射方法包括如下步骤。
1301、通过四个光源分别发射四路光束。
应理解，四路光束具有相同的初始偏振态且四路光束的波长各不相同，四路光束按照波长从小到大的顺序依次为第一光束、第二光束、第三光束和第四光束。
1302、通过第一合波单元对第一光束和第四光束进行合波得到第一合波光束，并对第二光束和第三光束进行合波得到第二合波光束。
需要说明的是，第一合波单元的具体实现方式可以参照上述图7(a)、图7(b)和图8所示实施例的相关介绍，此处不再赘述。
1303、通过偏振旋转单元对第一合波光束和第二合波光束中的至少一个合波光束进行偏振态调节。
应理解，经过偏振旋转单元后第一合波光束具有的第一偏振态与第二合波光束具有的第二偏振态垂直。需要说明的是，偏振旋转单元的具体实现方式可以参照上述图7(a)、图7(b)和图8所示实施例的相关介绍，此处不再赘述。
1304、通过第二合波单元对偏振旋转单元输出的第一合波光束和第二合波光束进行合波得到第三合波光束。
以上，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本申请的保护范围之内。

Claims (30)

  1. 一种光发射模块TOSA，其特征在于，包括：四个光源、偏振旋转单元和合波单元；
    所述四个光源用于分别发射四路光束，所述四路光束具有相同的初始偏振态且所述四路光束的波长各不相同，所述四路光束按照波长从小到下的顺序依次为第一光束、第二光束、第三光束和第四光束；
    所述偏振旋转单元用于对至少两路光束进行偏振态调节，以使得所述第一光束和所述第四光束具有的第一偏振态与所述第二光束和所述第三光束具有的第二偏振态垂直；
    所述合波单元用于对所述偏振旋转单元输出的四路光束进行合波得到合波光束。
  2. 根据权利要求1所述的TOSA，其特征在于，所述四路光束的初始偏振态为所述第一偏振态，所述偏振旋转单元用于将所述第二光束和所述第三光束调节为第二偏振态；
    或者，
    所述四路光束的初始偏振态为所述第二偏振态，所述偏振旋转单元用于将所述第一光束和所述第四光束调节为第一偏振态。
  3. 根据权利要求2所述的TOSA，其特征在于，所述偏振旋转单元包括第一偏振旋转元件和第二偏振旋转元件；
    若述四路光束的初始偏振态为所述第一偏振态，所述第一偏振旋转元件用于将所述第二光束调节为所述第二偏振态，所述第二偏振旋转元件用于将所述第三光束调节为所述第二偏振态；
    若述四路光束的初始偏振态为所述第二偏振态，所述第一偏振旋转元件用于将所述第一光束调节为所述第一偏振态，所述第二偏振旋转元件用于将所述第四光束调节为所述第一偏振态。
  4. 根据权利要求2或3所述的TOSA，其特征在于，所述TOSA还包括偏振不相关隔离器；
    所述偏振不相关隔离器用于透传所述合波光束并隔离所述合波光束的回波反射光束。
  5. 根据权利要求1所述的TOSA，其特征在于，所述偏振旋转单元用于将所述第一光束和所述第四光束由所述初始偏振态调节为所述第一偏振态，并将所述第二光束和所述第三光束由所述初始偏振态调节为所述第二偏振态。
  6. 根据权利要求5所述的TOSA，其特征在于，所述偏振旋转单元包括两个第一偏振旋转元件和两个第二偏振旋转元件；
    所述两个第一偏振旋转单元用于分别将所述第一光束和所述第四光束由所述初始偏振态调节为所述第一偏振态；
    所述两个第二偏振旋转元件用于分别将所述第二光束和所述第三光束由所述初始偏振态调节为所述第二偏振态。
  7. 根据权利要求6所述的TOSA，其特征在于，所述两个第一偏振旋转单元为第一偏振相关隔离器，所述两个第二偏振旋转单元为第二偏振相关隔离器；
    所述两个第一偏振旋转单元还用于分别隔离所述第一光束的回波反射光束和所述第四光束的回波反射光束；
    所述两个第二偏振旋转单元还用于分别隔离所述第二光束的回波反射光束和所述第三光束的回波反射光束。
  8. 根据权利要求1至7中任一项所述的TOSA，其特征在于，所述合波单元为z-block合波器。
  9. 根据权利要求1至8中任一项所述的TOSA，其特征在于，每个所述光源包括激光器和准直透镜；
    所述准直透镜用于对所述激光器发射的光束进行准直。
  10. 一种光发射模块TOSA，其特征在于，包括：四个光源、第一合波单元、偏振旋转单元和第二合波单元；
    所述四个光源用于分别发射四路光束，所述四路光束具有相同的初始偏振态且所述四路光束的波长各不相同，所述四路光束按照波长从小到下的顺序依次为第一光束、第二光束、第三光束和第四光束；
    所述第一合波单元用于对所述第一光束和所述第四光束进行合波得到第一合波光束，并对所述第二光束和所述第三光束进行合波得到第二合波光束；
    所述偏振旋转单元用于对所述第一合波光束和所述第二合波光束中的至少一个合波光束进行偏振 态调节，以使得所述第一合波光束具有的第一偏振态与所述第二合波光束具有的第二偏振态垂直；
    所述第二合波单元用于对所述偏振旋转单元输出的第一合波光束和第二合波光束进行合波得到第三合波光束。
  11. 根据权利要求10所述的TOSA，其特征在于，所述偏振旋转单元包括偏振旋转元件和偏振相关隔离器；
    所述偏振相关隔离器用于透传所述第一合波光束和所述第二合波光束，并隔离所述第一合波光束的回波反射光束和所述第二合波光束的回波反射光束；
    若所述四路光束的初始偏振态为所述第一偏振态，所述偏振旋转元件用于将所述偏振相关隔离器输出的第二合波光束调节为所述第二偏振态；
    若所述四路光束的初始偏振态为所述第二偏振态，所述偏振旋转元件用于将所述偏振相关隔离器输出的第一合波光束调节为所述第一偏振态。
  12. 根据权利要求10所述的TOSA，其特征在于，所述偏振旋转单元包括第一偏振旋转元件和第二偏振旋转元件；
    所述第一偏振旋转元件用于将所述第一合波光束由所述初始偏振态调节为所述第一偏振态；
    所述第二偏振旋转元件用于将所述第二合波光束由所述初始偏振态调节为所述第二偏振态。
  13. 根据权利要求12所述的TOSA，其特征在于，所述第一偏振旋转元件为第一偏振相关隔离器，所述第二偏振旋转元件为第二偏振相关隔离器；
    所述第一偏振旋转元件还用于隔离所述第一合波光束的回波反射光束；
    所述第二偏振旋转元件还用于隔离所述第二合波光束的回波反射光束。
  14. 根据权利要求10至13中任一项所述的TOSA，其特征在于，所述第一合波单元包括反射元件、第一合波元件和第二合波元件；
    所述反射元件用于对所述第一光束和所述第二光束进行反射；
    所述第一合波元件用于对经过反射的所述第一光束和所述第四光束进行合波得到所述第一合波光束；
    所述第二合波元件用于对经过反射的所述第二光束和所述第三光束进行合波得到所述第二合波光束；
    或者，
    所述反射元件用于对所述第三光束和所述第四光束进行反射；
    所述第一合波元件用于对所述第一光束和经过反射的所述第四光束进行合波得到所述第一合波光束；
    所述第二合波元件用于对所述第二光束和经过反射的所述第三光束进行合波得到所述第二合波光束。
  15. 根据权利要求10至14中任一项所述的TOSA，其特征在于，所述第二合波单元为偏振合波器PBC。
  16. 根据权利要求10至15中任一项所述的TOSA，其特征在于，每个所述光源包括激光器和准直透镜；
    所述准直透镜用于对所述激光器发射的光束进行准直。
  17. 一种光模块，其特征在于，包括：如权利要求1至16中任一项所述的TOSA、光接收模块ROSA和光纤连接端口；
    所述TOSA用于向所述光纤连接端口输出光束；
    所述ROSA用于接收来自所述光纤连接端口的光束。
  18. 一种光网络设备，其特征在于，包括如权利要求17所述的光模块，所述光模块集成在所述光网络设备中。
  19. 一种光发射方法，其特征在于，所述光发射方法应用于光发射模块TOSA，所述TOSA包括：四个光源、偏振旋转单元和合波单元；所述方法包括：
    通过所述四个光源分别发射四路光束，所述四路光束具有相同的初始偏振态且所述四路光束的波长各不相同，所述四路光束按照波长从小到下的顺序依次为第一光束、第二光束、第三光束和第四光束；
    通过所述偏振旋转单元对至少两路光束进行偏振态调节，以使得所述第一光束和所述第四光束具有的第一偏振态与所述第二光束和所述第三光束具有的第二偏振态垂直；
    通过所述合波单元对所述偏振旋转单元输出的四路光束进行合波得到合波光束。
  20. 根据权利要求19所述的方法，其特征在于，所述四路光束的初始偏振态为所述第一偏振态，通过所述偏振旋转单元对至少两路光束进行偏振态调节包括：
    通过所述偏振旋转单元将所述第二光束和所述第三光束调节为第二偏振态；
    或者，
    所述四路光束的初始偏振态为所述第二偏振态，通过所述偏振旋转单元对至少两路光束进行偏振态调节包括：
    通过所述偏振旋转单元将所述第一光束和所述第四光束调节为第一偏振态。
  21. 根据权利要求20所述的方法，其特征在于，所述偏振旋转单元包括第一偏振旋转元件和第二偏振旋转元件，通过所述偏振旋转单元对至少两路光束进行偏振态调节包括：
    若述四路光束的初始偏振态为所述第一偏振态，通过所述第一偏振旋转元件将所述第二光束调节为所述第二偏振态，通过所述第二偏振旋转元件将所述第三光束调节为所述第二偏振态；
    若述四路光束的初始偏振态为所述第二偏振态，通过所述第一偏振旋转元件将所述第一光束调节为所述第一偏振态，通过所述第二偏振旋转元件将所述第四光束调节为所述第一偏振态。
  22. 根据权利要求20或21所述的方法，其特征在于，所述TOSA还包括偏振不相关隔离器，所述方法还包括：
    通过所述偏振不相关隔离器透传所述合波光束并隔离所述合波光束的回波反射光束。
  23. 根据权利要求19所述的方法，其特征在于，通过所述偏振旋转单元对至少两路光束进行偏振态调节包括：
    通过所述偏振旋转单元将所述第一光束和所述第四光束由所述初始偏振态调节为所述第一偏振态，并将所述第二光束和所述第三光束由所述初始偏振态调节为所述第二偏振态。
  24. 根据权利要求23所述的方法，其特征在于，所述偏振旋转单元包括两个第一偏振旋转元件和两个第二偏振旋转元件，通过所述偏振旋转单元对至少两路光束进行偏振态调节包括：
    通过所述两个第一偏振旋转单元分别将所述第一光束和所述第四光束由所述初始偏振态调节为所述第一偏振态；
    通过所述两个第二偏振旋转元件分别将所述第二光束和所述第三光束由所述初始偏振态调节为所述第二偏振态。
  25. 根据权利要求24所述的方法，其特征在于，所述两个第一偏振旋转单元为第一偏振相关隔离器，所述两个第二偏振旋转单元为第二偏振相关隔离器，所述方法还包括：
    通过所述两个第一偏振旋转单元还分别隔离所述第一光束的回波反射光束和所述第四光束的回波反射光束；
    通过所述两个第二偏振旋转单元还分别隔离所述第二光束的回波反射光束和所述第三光束的回波反射光束。
  26. 一种光发射方法，其特征在于，所述光发射方法应用于光发射模块TOSA，所述TOSA包括：四个光源、第一合波单元、偏振旋转单元和第二合波单元；所述方法包括：
    通过所述四个光源分别发射四路光束，所述四路光束具有相同的初始偏振态且所述四路光束的波长各不相同，所述四路光束按照波长从小到下的顺序依次为第一光束、第二光束、第三光束和第四光束；
    通过所述第一合波单元对所述第一光束和所述第四光束进行合波得到第一合波光束，并对所述第二光束和所述第三光束进行合波得到第二合波光束；
    通过所述偏振旋转单元对所述第一合波光束和所述第二合波光束中的至少一个合波光束进行偏振态调节，以使得所述第一合波光束具有的第一偏振态与所述第二合波光束具有的第二偏振态垂直；
    通过所述第二合波单元对所述偏振旋转单元输出的第一合波光束和第二合波光束进行合波得到第三合波光束。
  27. 根据权利要求26所述的方法，其特征在于，所述偏振旋转单元包括偏振旋转元件和偏振相关隔 离器，通过所述偏振旋转单元对所述第一合波光束和所述第二合波光束中的至少一个合波光束进行偏振态调节包括：
    通过所述偏振相关隔离器透传所述第一合波光束和所述第二合波光束，并隔离所述第一合波光束的回波反射光束和所述第二合波光束的回波反射光束；
    若所述四路光束的初始偏振态为所述第一偏振态，通过所述偏振旋转元件将所述偏振相关隔离器输出的第二合波光束调节为所述第二偏振态；
    若所述四路光束的初始偏振态为所述第二偏振态，通过所述偏振旋转元件将所述偏振相关隔离器输出的第一合波光束调节为所述第一偏振态。
  28. 根据权利要求26所述的方法，其特征在于，所述偏振旋转单元包括第一偏振旋转元件和第二偏振旋转元件，通过所述偏振旋转单元对所述第一合波光束和所述第二合波光束中的至少一个合波光束进行偏振态调节包括：
    通过所述第一偏振旋转元件将所述第一合波光束由所述初始偏振态调节为所述第一偏振态；
    通过所述第二偏振旋转元件将所述第二合波光束由所述初始偏振态调节为所述第二偏振态。
  29. 根据权利要求28所述的方法，其特征在于，所述第一偏振旋转元件为第一偏振相关隔离器，所述第二偏振旋转元件为第二偏振相关隔离器，所述方法还包括：
    通过所述第一偏振旋转元件隔离所述第一合波光束的回波反射光束；
    通过所述第二偏振旋转元件隔离所述第二合波光束的回波反射光束。
  30. 根据权利要求26至29中任一项所述的方法，其特征在于，所述第一合波单元包括反射元件、第一合波元件和第二合波元件，通过所述第一合波单元对所述第一光束和所述第四光束进行合波得到第一合波光束，并对所述第二光束和所述第三光束进行合波得到第二合波光束包括：
    通过所述反射元件对所述第一光束和所述第二光束进行反射；
    通过所述第一合波元件对经过反射的所述第一光束和所述第四光束进行合波得到所述第一合波光束；
    通过所述第二合波元件对经过反射的所述第二光束和所述第三光束进行合波得到所述第二合波光束；
    或者，
    通过所述反射元件对所述第三光束和所述第四光束进行反射；
    通过所述第一合波元件对所述第一光束和经过反射的所述第四光束进行合波得到所述第一合波光束；
    通过所述第二合波元件对所述第二光束和经过反射的所述第三光束进行合波得到所述第二合波光束。
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