A long-haul transmission coherent optical module, channel and communication method

Abstract

This invention specifically relates to a coherent optical module, path, and communication method for long-distance transmission. The optical module includes: a transmitter: comprising a signal generator, a first digital processor sequentially arranged in the signal processing path, a modulator, a coupler, an erbium-doped fiber, a filter, a transmitter port, and a pump laser source connected to the coupler; a receiver: comprising a receiver port that sequentially processes the received signal light, an integrated coherent receiver, and a signal receiver; and a tunable laser for generating and splitting a laser beam, one beam being the signal light, which enters the modulator in the transmitter; and the other beam being the intrinsic light, which enters the integrated coherent receiver in the receiver. This invention utilizes the pump laser source, erbium-doped fiber, and coupler to amplify the signal light, increasing its optical power. Simultaneously, a filter reduces the noise of the amplified signal light, and the laser light provided by the pump laser source is filtered to improve the signal-to-noise ratio of the signal light.

Description

Technical Field

[0001] This invention relates to the field of coherent optical communication technology, specifically to a coherent optical module, path, and communication method for long-distance transmission. Background Technology

[0002] Coherent optical communication is an advanced optical transmission technology that uses parameters such as the phase, amplitude, polarization, and frequency of light waves to carry information, thereby achieving high-speed, long-distance, and high-capacity optical communication. This technology has broad application prospects in backbone networks, metropolitan area networks, and space communication.

[0003] Furthermore, the application of higher-order modulation formats in coherent optical communication results in higher single-wavelength channel spectral efficiency compared to traditional communication systems. Coherent receivers also have no special requirements for fiber optic channels, allowing for the reuse of existing fiber optic lines. Coherent optical communication utilizes digital signal processing algorithms, enabling coherent receivers to compensate for signal distortion caused by fiber dispersion, polarization mode dispersion, and carrier phase noise at minimal cost. However, existing coherent optical communication technologies face the challenge of increasing transmission distance. For example, in ultra-long-distance transmissions exceeding 100km from a single point to a point, coherent optical communication is prone to problems such as high noise interference and insufficient receiver sensitivity. Summary of the Invention

[0004] This invention addresses the technical problem that coherent optical communication transmission in the prior art is difficult to achieve ultra-long-distance transmission across a single point, and provides a coherent optical module for long-distance transmission, which has at least the advantages of low signal interference and high sensitivity.

[0005] In a first aspect, the present invention provides a coherent optical module for long-distance transmission, comprising:

[0006] The transmitting end includes a signal generator, a first digital processor arranged sequentially in the signal processing path, a modulator, a coupler, an erbium-doped fiber, a filter, a transmitting port, and a pump laser source connected to the coupler;

[0007] Receiver: Includes a receiver port that processes the received signal light sequentially, an integrated coherent receiver, and a signal receiver;

[0008] A tunable laser is used to generate and split a laser beam, one of which is a signal beam that enters the modulator in the transmitter; the other is an intrinsic beam that enters the integrated coherent receiver in the receiver.

[0009] Specifically, one of the main concepts of this invention is to amplify the signal light using a pump laser source, erbium-doped fiber, and coupler to increase the optical power of the signal light. At the same time, a filter is used to reduce the noise of the signal light after power amplification, and the laser provided by the pump laser source is filtered to improve the signal-to-noise ratio of the signal light. This achieves the purpose of increasing the output optical power and output noise of the signal light, thereby making this invention suitable for long-distance transmission of more than 100km from point to point.

[0010] Optionally, a driver is provided between the digital processor and the modulator.

[0011] Optionally, an isolator is provided between the erbium-doped fiber and the filter.

[0012] Furthermore, a variable optical attenuator is provided after the isolator.

[0013] Specifically, the variable optical attenuator adjusts the optical power by changing the attenuation of the signal light, so that the present invention can adjust the attenuation as needed to ensure that the optical power falls within the receiving range of the receiving end. Thus, the present invention can be configured with different attenuation amounts according to the transmission distance to adapt to single-point-to-point transmission of signal light at different transmission distances.

[0014] Optionally, an optical power detector is provided between the filter and the transmission port.

[0015] Optionally, a second digital processor is provided between the integrated coherent receiver and the signal receiver.

[0016] Furthermore, a transimpedance amplifier is provided after the integrated coherent receiver.

[0017] In a second aspect, the present invention provides a long-distance coherent optical path, comprising a long-distance coherent optical module as described in any embodiment of the first aspect, including:

[0018] The coherent optical module is located at both ends and serves as a transmitter and receiver for each other.

[0019] Two transmission optical fibers are provided, one end of which is connected to the transmitter of one coherent optical module and the other end of which is connected to the receiver of another coherent optical module; one end of the other transmission optical fiber is connected to the receiver of one coherent optical module and the other end of which is connected to the transmitter of another coherent optical module.

[0020] Specifically, the coherent optical path provided by the present invention realizes bidirectional coherent optical communication from point to point through the coherent optical modules that are mutually transmitting and receiving ends.

[0021] Thirdly, the present invention provides a long-distance coherent optical communication method, used in a long-distance coherent optical module as described in any embodiment of the first aspect, or in a long-distance coherent optical path as described in any embodiment of the second aspect, comprising the following steps:

[0022] At the aforementioned transmitting end:

[0023] S100, the signal generator generates a first electrical signal, and the first electrical signal is processed by the first digital processor;

[0024] S110. The tunable laser generates a first signal light, which enters the modulator, and the first electrical signal is loaded onto the first signal light by the driver.

[0025] S120. The pump laser source is used to provide particle energy, and under the action of the coupler, the first signal light in the preset wavelength range is amplified through the erbium-doped fiber.

[0026] S130. The amplified first signal light is filtered by the filter and then emitted through the transmission port.

[0027] At the receiving end:

[0028] S200: The receiving port receives the second signal light, and then the integrated coherent receiver beats the second signal light to obtain the second electrical signal.

[0029] S210, The signal receiver receives the electrical signal.

[0030] Furthermore, after step S120, step S121 is included;

[0031] S121. Optical isolation of the signal light is achieved by using an isolator.

[0032] In summary, the present invention provides a coherent optical module, path, and communication method for long-distance transmission, which has at least the following advantages:

[0033] 1. This invention utilizes a pump laser source, erbium-doped fiber, and coupler to amplify the signal light, thereby increasing the optical power of the signal light. At the same time, it uses a filter to reduce the noise of the signal light after power amplification and filters the laser provided by the pump laser source to improve the signal-to-noise ratio of the signal light. This achieves the purpose of increasing the output optical power and output noise of the signal light, thus making this invention suitable for long-distance transmission of more than 100km from point to point.

[0034] 2. This invention uses a variable optical attenuator to adjust the optical power by changing the attenuation of the signal light. This allows the invention to adjust the attenuation as needed to ensure that the optical power falls within the receiving range of the receiving end. As a result, this invention can be configured with different attenuation values ​​according to the transmission distance to adapt to single-point-to-point transmission of signal light at different transmission distances. Attached Figure Description

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, those skilled in the art will understand that these drawings are drawn only for the purpose of explaining the preferred embodiments and therefore should not be construed as limiting the scope of the invention. Furthermore, unless specifically indicated, the drawings are only schematic representations of the composition or structure of the described objects and may contain exaggerated depictions, and the drawings are not necessarily drawn to scale.

[0036] Figure 1 A schematic diagram of the composition of a coherent optical module for long-distance transmission provided in an embodiment of the present invention;

[0037] Figure 2 A test block diagram for single-span point-to-point transmission provided in an embodiment of the present invention;

[0038] Figure 3 The optical power test diagram of the signal light at the transmitting end provided in the embodiment of the present invention;

[0039] Figure 4 A sensitivity test diagram of the signal light at the receiving end provided in an embodiment of the present invention;

[0040] Figure 5 A schematic diagram of the composition of a coherent optical path for long-distance transmission provided by an embodiment of the present invention;

[0041] Figure 6 A flowchart illustrating a long-distance coherent optical communication method provided in this embodiment of the invention. Detailed Implementation

[0042] The following is in conjunction with the appendix Figures 1 to 6 The present invention will be described in detail below.

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0044] The main concept of this invention is to amplify the signal light using a pump laser source, erbium-doped fiber, and coupler to increase the optical power of the signal light. At the same time, a filter is used to reduce the noise of the signal light after power amplification, and the laser provided by the pump laser source is filtered to improve the signal-to-noise ratio of the signal light. Thus, this invention is suitable for long-distance transmission of more than 100km from point to point.

[0045] For an explanation of the structural composition of the optical module provided by this invention, please refer to [link / reference]. Figure 1 The diagram shown is a schematic representation of a coherent optical module for long-distance transmission provided in an embodiment of the present invention.

[0046] Specifically, the explanations of each component are as follows:

[0047] Signal generator: In order to realize bit error testing in optical communication system, the signal generator is a code generator that inputs high-speed modulated signal to the transmitter of DSP;

[0048] First Digital Signal Processor (DSP): When signal light is transmitted in an optical fiber link, distortion will occur. Digital signal processors take advantage of the fact that digital signals are relatively easy to process to amplify, shape, and make decisions on the signal to counteract and compensate for the distortion and reduce the impact of distortion on the system bit error rate. Among them, the first digital signal processor is used to convert electrical signals into digital signals.

[0049] Driver: Used to work in conjunction with the first digital processor (DSP) to preprocess and postprocess the signal light, including dispersion compensation, nonlinear compensation, etc., to improve the signal reception quality and system reliability;

[0050] Modulator: The Mach-Zehnder modulator (MZ modulator) is a typical external modulator in optical communication systems. It is a structure in which two phase modulators are used in parallel to generate interference. The modulation of the signal light is achieved by controlling the phase in the signal optical path.

[0051] Pump laser source (PUMP laser): Used to provide energy to erbium-doped fiber, exciting the ground-state erbium ions to a high-energy state, causing population inversion, thereby stimulated emission and amplifying the signal light within a preset wavelength range;

[0052] The preset wavelength range is 1450nm~1650nm.

[0053] Coupler: A WDM coupler with an isolator (IS / WDM) couples the weak input signal light to be amplified and the output light wave from the pump laser source into the erbium-doped fiber. The wavelength division multiplexer (WDM), combined with the isolator at its input, prevents light reflection from affecting the pump laser source.

[0054] Erbium-doped fiber: A silica fiber doped with a small amount of the rare earth element erbium (Er) ions. When stimulated emission, it will produce energy level transitions and emit photons that are exactly the same as the input excitation photons, thus amplifying the light.

[0055] Isolator: It is a device that prevents reflected light from affecting the working stability of the optical amplifier, ensuring that the signal light can only be transmitted in the forward direction and is not affected by backscattered light, so as to stably and normally amplify the signal light;

[0056] Variable Optical Attenuator (VOA): An important passive optical device used to adjust the intensity of optical signals. It achieves real-time control of the signal by changing the amount of attenuation of the signal light.

[0057] Time-of-Flight (TOF) filters are used to filter out noise from optical amplifiers, achieve better out-of-band OSNR, reduce the impact of noise on the system, improve the signal-to-noise ratio of the system, and also filter out the light from the pump laser source (PUMP laser).

[0058] Optical power detector (TAP / PD): The signal light is split into two, with 99% of the light being emitted and 1% entering the photodiode to achieve optical power detection; the 99:1 separation ratio is the standard setting, but other separation ratios can also be adopted;

[0059] Transmit port (TX): Used to transmit signal light;

[0060] Receive port (RX): Used to receive signal light;

[0061] Integrated Coherent Receiver (ICR): Generates a beat frequency signal by combining the local oscillator light with the signal light, and demodulates the phase-correlated modulated signal light.

[0062] A transimpedance amplifier (TIA) converts photocurrent into a small-voltage digital signal; it is a linear small-signal amplifier that achieves the conversion from light to electricity.

[0063] Second digital processor (DSP): Used to convert optical signals into electrical signals;

[0064] Signal receiver: Receives and detects signal errors; used for signal detection and decision-making.

[0065] Tunable laser (ITLA, Integrable Tunable Laser Assembly): Used to output a narrowband light source with tunable wavelength. The light source is split into two beams. One beam enters the modulator as the signal light, and the other beam enters the integrated coherent receiver as the intrinsic optomechanical system.

[0066] Example 1: Transmitter ( Figure 1The upper dashed box includes a signal generator, a first digital processor, a modulator, a coupler, an erbium-doped fiber, a filter, a transmitter port, and a pump laser source; the receiver ( Figure 1 The component shown in the lower dashed box includes a receiving port, an integrated coherent receiver and a signal receiver; and a tunable laser; the components within the outermost solid box constitute the optical module.

[0067] Its working principle is as follows: The tunable laser generates two beams of light, one used as the signal beam and the other as the intrinsic beam. The signal beam enters the transmitting end, where a digital signal is loaded onto it by a signal generator and a first digital processor. The signal beam is then modulated by a modulator, and further amplified by a pump laser source, coupler, and erbium-doped laser to increase its emitted power. Simultaneously, an isolator (IS / WDM) is installed at the front end of the coupler to prevent the pump laser source from being affected by reflected light. The amplified signal beam is then filtered to remove noise and the emitted light waves from the pump laser source. Finally, the signal beam is emitted through the transmitting port. Because the combined use of the pump laser source, coupler, and erbium-doped fiber increases the emitted power of the signal beam, and the filter performs signal-to-noise filtering on the amplified beam, the signal beam, after passing through the transmitting port, is suitable for long-distance transmission, achieving point-to-point transmission distances exceeding 100 km.

[0068] Example 2: In addition to the devices in Example 1, the transmitter also includes a driver, an isolator, a variable attenuator, and an optical power detector; in addition to the devices in Example 1, the receiver also includes a transimpedance amplifier and a second signal processor (see [link to example 1]). Figure 1 As shown, Example 1 provides a minimum standard implementation of the present invention;

[0069] Its working principle is as follows: At the transmitting end, an isolator located after the erbium-doped fiber provides optical isolation for the amplified signal light within the erbium-doped fiber, preventing scattering caused by the emission of high-power signal light and improving the stability of the amplified signal light. Furthermore, a variable optical attenuator located after the filter adjusts the intensity of the filtered signal light to make it suitable for long-distance transmission. An optical power detector located before the transmitting port primarily detects the power of the signal light to be transmitted, ensuring that the optical power of the signal light emitted from the transmitting port meets the requirements for long-distance transmission. At the receiving end, a transimpedance amplifier located after the integrated coherent receiver amplifies the signal light after attenuation during long-distance transmission, and a second signal processor located before the signal receiver converts the signal light into an electrical signal for use.

[0070] Because the optical module's transmitting end has a large output power, normally exceeding +5dBm, and employs coherent demodulation technology with ultra-high receiving sensitivity, it can directly achieve point-to-point transmission of over 100km in a 400G optical transmission system without the need for an external optical amplifier, and in a 100G system, it can directly achieve point-to-point transmission of over 160km.

[0071] In addition, the variable optical attenuator integrated at the transmitter filters out out-of-band noise, achieving higher in-band and out-of-band OSNR. In scenarios without external filters, multiple wavelengths can be transmitted simultaneously, simplifying the fiber optic system deployment architecture and reducing the construction cost of long-distance optical transmission systems.

[0072] For further details, please see Figure 2 The diagram shown is a test block diagram for single-span point-to-point transmission provided in an embodiment of the present invention.

[0073] Specifically, Figure 2 The diagram shows that the optical signal from the transmitter of the optical module under test is coupled to the noise of ASE (amplified spontaneous emission) through a coupler into an optical fiber. After transmission through 100km of single-mode fiber, the signal is amplified by an EDFA (optical amplifier). The resulting optical signal is split into two parts in a 50:50 ratio. One part is sent to an OSA (Optical Subsystem Assembly) to test the OSNR (Optical Signal-to-Noise Ratio), while the other part passes through a WSS (Wavelength Selective Switch) filter and returns to the RX end of the module to test its performance.

[0074] For further details, please see Figure 3 The figure shown is a test diagram of the optical power of the signal light at the transmitting end provided in an embodiment of the present invention.

[0075] Specifically, Figure 3 The paper presents data on the TX output optical power of modules with different SN (Signal-to-Noise Ratio) values ​​under 16QAM, 400G testing conditions, at different wavelengths of 191.3 Hz, 193.7 Hz, and 196.1 Hz, and at different temperatures of 0°C, 45°C, and 75°C. Based on the figures, the optical module provided by this invention exhibits a signal-to-noise ratio that is generally concentrated between 5 dBm and 7 dBm after long-distance transmission, meeting the requirements for long-distance optical communication.

[0076] For further details, please see Figure 4 The figure shown is a sensitivity test diagram of the signal light at the receiving end provided in an embodiment of the present invention.

[0077] Specifically, Figure 4 The data presented show the RX sensitivity of modules with different signal sources at different wavelengths (191.3 THz, 193.7 THz, and 196.1 THz) and at different temperatures (0℃, 45℃, and 75℃). Based on the figures, the receiver sensitivity of the optical module provided by this invention is basically concentrated between -23 dBm and -27 dBm after long-distance transmission, which meets the requirements of long-distance optical communication.

[0078] To further explain the application scenarios of the optical module provided by this invention, please refer to [link / reference]. Figure 5 The diagram shown is a schematic representation of the composition of a long-distance coherent optical path provided by an embodiment of the present invention.

[0079] Specifically, the optical module provided by this invention only requires a symmetrical design on both sides and can directly use existing transmission optical fibers, making it highly adaptable. The transmitting port of one optical module emits signal light, which enters the receiving port of another optical module via the transmission optical fiber to complete optical communication; while its receiving port receives signal light from the transmitting port of the other optical module, thereby realizing bidirectional communication.

[0080] For further details, please see Figure 6 The diagram shown is a flowchart of a long-distance coherent optical communication method provided by an embodiment of the present invention.

[0081] Specifically, the transmitting end includes at least the following steps: S100, generating an electrical signal through the signal generator and processing the electrical signal through the first digital processor; S110, generating signal light through the tunable laser, which enters the modulator, and the driver loads the electrical signal onto the signal light; S120, providing particle energy through the pump laser source, and amplifying the signal light within a preset wavelength range through the erbium-doped fiber under the action of the coupler; S130, filtering the amplified signal light through the filter, and then transmitting the signal light through the transmitting port.

[0082] The transmitted signal light is received through the receiving port of the receiving end. The receiving end includes at least the following steps: S200, the receiving port receives the signal light, and then the integrated coherent receiver beats the signal light to obtain an electrical signal; S210, the signal receiver receives the electrical signal.

[0083] Furthermore, after step S120, step S121 is included;

[0084] S121. Optical isolation of the signal light is achieved by using an isolator.

[0085] The present invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of the embodiments above are only for the purpose of helping to understand the invention and its core ideas. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A coherent optical module for long-distance transmission, characterized in that, include: The transmitting end includes a signal generator, a first digital processor arranged sequentially in the signal processing path, a modulator, a coupler, an erbium-doped fiber, a filter, a transmitting port, and a pump laser source connected to the coupler; Receiver end: includes a receiving port that processes the received signal light in sequence, an integrated coherent receiver, and a signal receiver; A tunable laser is used to generate and split a laser beam, one of which is a signal beam for entering the modulator in the transmitter. The other is intrinsic light, which is used to enter the integrated coherent receiver in the receiving end.

2. The coherent optical module for long-distance transmission as described in claim 1, characterized in that, A driver is provided between the first digital processor and the modulator.

3. The long-distance transmission coherent optical module as described in claim 1, characterized in that, An isolator is provided between the erbium-doped fiber and the filter.

4. The long-distance transmission coherent optical module as described in claim 3, characterized in that, A variable optical attenuator is provided after the isolator.

5. The coherent optical module for long-distance transmission as described in claim 1, characterized in that, An optical power detector is provided between the filter and the transmission port.

6. The coherent optical module for long-distance transmission as described in claim 1, characterized in that, A second digital processor is provided between the integrated coherent receiver and the signal receiver.

7. A coherent optical module for long-distance transmission as described in claim 6, characterized in that, A transimpedance amplifier is provided after the integrated coherent receiver.

8. A long-distance coherent optical path, comprising a long-distance coherent optical module as described in any one of claims 1-7, characterized in that, include: The coherent optical module is located at both ends and serves as a transmitter and receiver for each other. Two transmission optical fibers are provided, one end of which is connected to the transmitter of one coherent optical module and the other end of which is connected to the receiver of another coherent optical module; one end of the other transmission optical fiber is connected to the receiver of one coherent optical module and the other end of which is connected to the transmitter of another coherent optical module.

9. A long-distance coherent optical communication method, used in a long-distance coherent optical module as described in any one of claims 1-7, or used in a long-distance coherent optical path as described in claim 8, characterized in that, Includes the following steps: At the aforementioned transmitting end: S100, the signal generator generates a first electrical signal, and the first electrical signal is processed by the first digital processor; S110. The tunable laser generates a first signal light, which enters the modulator, and the first electrical signal is loaded onto the first signal light by the driver. S120. The pump laser source is used to provide particle energy, and under the action of the coupler, the first signal light in the preset wavelength range is amplified through the erbium-doped fiber. S130. The amplified first signal light is filtered by the filter and then emitted through the transmission port. At the receiving end: S200: The receiving port receives the second signal light, and then the integrated coherent receiver beats the second signal light to obtain the second electrical signal. S210, The signal receiver receives the second electrical signal.

10. The long-distance coherent optical communication method as described in claim 9, characterized in that, After step S120, step S121 is included; S121. Optical isolation of the signal light is achieved by using an isolator.

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