A directly modulated and directly detected optical transmission system and method

Abstract

The application discloses a direct modulation and direct detection optical transmission system and an optical transmission method, and relates to the technical field of optical communication. Different wavelength modulation optical signals generated by multiple direct modulation and direct detection optical modules are combined into one multiplexed optical signal by adopting an external combiner, and the external combiner is used for wavelength division at the receiving end, so that the multiple direct modulation and direct detection optical modules originally occupying one optical fiber independently can share one hollow core optical fiber for transmission, thereby the number of wave channels in the single fiber is expanded by increasing the number of optical modules without increasing the number of optical fibers, and the transmission capacity of the single fiber is improved. In addition, by adopting the hollow core optical fiber as the transmission medium, the low dispersion characteristics of the hollow core optical fiber in the C band and the L band are utilized, so that the direct modulation and direct detection optical module can work in the C band and the L band, and then the rich wavelength resources in the C band and the L band can be utilized to realize dense wavelength division multiplexing, the single fiber transmission capacity is further improved, and the increasing capacity demand between data centers is met.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, and in particular to a direct-modulation, direct-detection optical transmission system and optical transmission method. Background Technology

[0002] Intensity modulation and direct-detection (IMDD) optical transmission systems are widely used in short-distance optical transmission scenarios such as data center optical interconnects due to their advantages of low cost, low power consumption, and low latency.

[0003] Currently available commercially available direct-modulation and direct-detection optical modules mainly operate in the O-band. Taking a typical 800G optical module as an example, it uses four wavelengths in the O-band, with a single-wavelength rate of 200Gb / s, and achieves a single-fiber transmission capacity of 800Gb / s through coarse wavelength division multiplexing. Figure 1 This is a schematic diagram of a traditional O-band direct-modulation and direct-detection optical module and a coarse wavelength division multiplexing optical transmission system, as shown below. Figure 1 As shown, the external input electrical signal first enters the digital signal processor of the direct-modulation and direct-detection optical module 1, and after being amplified by the driver, drives the modulator to generate an optical modulation signal. An optical module typically integrates 4 or 8 wavelengths. Each wavelength is modulated separately and then sent to the silica fiber 2 for transmission via a multiplexer. At the receiving end, the signal transmitted via the silica fiber 2 is separated by a demultiplexer, and then converted from optical to electrical signals by a photodetector. After being amplified by a transimpedance amplifier, it is sent to the digital signal processor and output to external devices. Because this system typically only has 4 or 8 wavelengths, and the spacing between wavelengths is relatively large, it can only support coarse wavelength division multiplexing (CWDM) optical transmission systems, greatly limiting the optical transmission capacity of a single fiber and failing to meet the ever-increasing capacity demands of data centers.

[0004] Therefore, improving the optical transmission capacity of a single fiber is a technical problem that urgently needs to be solved by those in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a direct-modulation and direct-detection optical transmission system and optical transmission method to solve the technical problem of limited single-fiber optical transmission capacity in traditional O-band direct-modulation and direct-detection optical modules and coarse wavelength division multiplexing optical transmission systems.

[0006] To solve the above-mentioned technical problems, the present invention provides a direct-modulation, direct-detection optical transmission system, comprising: Multiple direct-modulation and direct-detection optical modules, each of which is used to generate a C-band or L-band modulated optical signal; An external multiplexer is connected to the output of the multiple direct-modulation and direct-detection optical modules to combine the modulated optical signals of different wavelengths output by the multiple direct-modulation and direct-detection optical modules into a single multiplexed optical signal. A hollow optical fiber is connected to the output end of the external multiplexer to transmit the multiplexed optical signal; An external wavelength division multiplexer is connected to the output end of the hollow optical fiber to separate the multiplexed optical signal into modulated optical signals of different wavelengths and output them to the corresponding direct-modulation and direct-detection optical modules.

[0007] Preferably, the wavelengths of the plurality of direct-modulation and direct-detection optical modules cover the entire C-band and L-band.

[0008] Preferably, each of the direct-modulation and direct-detection optical modules includes a digital signal processor, a driver, a modulator, a photodetector, and a transimpedance amplifier; The externally input electrical signal is processed by the digital signal processor and then sent to the driver for amplification. The amplified electrical signal drives the modulator to generate the modulated optical signal. The modulated optical signal from the external wavelength divider is converted into an electrical signal by the photodetector, amplified by the transimpedance amplifier, and then sent to the digital signal processor for output to an external device.

[0009] Preferably, the modulator is a Mach-Zehnder modulator, and a continuous wave laser is also provided outside the direct-modulation and direct-detection optical module to provide a continuous wave optical carrier to the Mach-Zehnder modulator; The continuous wave laser employs an integrated tunable laser assembly.

[0010] Preferably, the integrated tunable laser assembly is provided with a thermoelectric cooler for controlling the temperature drift of the continuous wave laser.

[0011] Preferably, the direct-modulation and direct-detection optical module is provided with a laser input interface, a modulation signal output interface, and a receiving optical signal input interface, and the laser input interface, modulation signal output interface, and receiving optical signal input interface all adopt multi-core push-pull interface.

[0012] Preferably, the transmission link of the hollow optical fiber is further provided with an erbium-doped fiber amplifier, which is used to amplify the power of the multiplexed optical signal.

[0013] Preferably, the integrated tunable laser assembly has a wavelength that is tunable throughout the entire C-band and L-band, so that a single direct-modulation and direct-detection optical module can cover any wavelength in the C-band and L-band.

[0014] Preferably, the modulator is a direct-modulated laser or an electro-absorption modulated laser; The externally input electrical signal is amplified by the driver and directly drives the direct modulation laser or the electroabsorption modulation laser to generate the modulation optical signal.

[0015] To address the aforementioned technical problems, the present invention also provides a direct-modulation direct-detection optical transmission method, applied to the aforementioned direct-modulation direct-detection optical transmission system, the method comprising: Multiple direct-modulation and direct-detection optical modules are used to generate modulated optical signals of different wavelengths in the C-band or L-band respectively; The modulated optical signals of different wavelengths output from the multiple direct-modulation and direct-detection optical modules are combined into a single multiplexed optical signal by an external multiplexer. The multiplexed optical signal is transmitted through a hollow optical fiber; The multiplexed optical signal transmitted through hollow optical fiber is separated into modulated optical signals of different wavelengths by an external wavelength divider, and then output to the corresponding direct-modulation and direct-detection optical modules for reception.

[0016] The direct-modulation direct-detection optical transmission system provided by this invention combines different wavelength modulated optical signals generated by multiple direct-modulation direct-detection optical modules into a single multiplexed optical signal using an external multiplexer, and performs wavelength division at the receiving end using an external demultiplexer. This allows multiple direct-modulation direct-detection optical modules, which originally each occupied an independent optical fiber, to share the same hollow-core optical fiber for transmission. Thus, without increasing the number of optical fibers, the number of channels within a single fiber is expanded by increasing the number of optical modules, significantly improving the transmission capacity of a single fiber. Furthermore, by using hollow-core optical fiber as the transmission medium and leveraging its low dispersion characteristics in the C-band and L-band, the direct-modulation and direct-detection optical module can operate in both the C-band and L-band. This allows for the utilization of the abundant wavelength resources in the C-band and L-band to achieve dense wavelength division multiplexing (DWDM), further improving the single-fiber transmission capacity. This effectively solves the technical problem of limited single-fiber transmission capacity in existing coarse wavelength division multiplexing systems due to the limited number of wavelengths, meeting the ever-increasing capacity demands of data centers while avoiding the increased cabling complexity and maintenance costs associated with simply increasing the number of optical fibers.

[0017] In addition, the present invention also provides a direct modulation and direct detection optical transmission method, which has the same or corresponding technical features as the aforementioned direct modulation and direct detection optical transmission system, and has the same effect. Attached Figure Description

[0018] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a traditional O-band direct-modulation and direct-detection optical module and a coarse wavelength division multiplexing optical transmission system. Figure 2 A schematic diagram of a direct-modulation, direct-detection optical transmission system provided in an embodiment of the present invention; Figure 3 This is a structural diagram of an external direct-modulation and direct-detection optical module for C and L band ITLA provided in an embodiment of the present invention; Figure 4 This is a flowchart of a direct-modulation and direct-detection optical transmission method provided in an embodiment of the present invention.

[0020] The attached figures are labeled as follows: 1-Direct-modulation and direct-detection optical module; 2-Quartz optical fiber; 3-Multiplexer; 4-Hollow-core optical fiber; 5-Demultiplexer; 6-Tunable laser array; 7-Thermoelectric cooler. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention.

[0022] The core of this invention is to provide a direct-modulation, direct-detection optical transmission system and optical transmission method to solve the technical problem of limited single-fiber optical transmission capacity in traditional O-band direct-modulation, direct-detection optical modules and coarse wavelength division multiplexing optical transmission systems.

[0023] Figure 1 Traditional O-band direct-modulation and direct-detection optical modules and coarse wavelength division multiplexing (CWDM) optical transmission systems typically only support 4 or 8 wavelengths with large wavelength intervals, severely limiting the single-fiber optical transmission capacity. The increasing demand for data transmission capacity between data centers makes increasing the number of optical fibers for capacity improvement unsustainable due to significant cabling and maintenance challenges. While DWDM can significantly increase single-fiber capacity, the high loss of O-band silica fiber, the lack of DWDM optical transmission devices, and the strong nonlinearity of the fiber make DWDM optical transmission systems difficult to apply. Although C- and L-band silica fibers have low loss and mature DWDM optical transmission devices, their large dispersion and power attenuation at the receiver make error-free transmission difficult. Furthermore, the power consumption limitations of existing optical modules prevent the integration of thermoelectric coolers (TECs) to control laser temperature, hindering the achievement of wavelength stability requirements in DWDM systems.

[0024] Therefore, this invention utilizes the characteristics of hollow-core optical fiber—low attenuation, low dispersion, and low nonlinearity in the C and L bands—to propose a DWDM hollow-core optical fiber interconnect system covering both the C and L bands, which can significantly increase the single-fiber transmission capacity of the direct-tuning and direct-detection system by more than 10 times. This invention also proposes a direct-tuning and direct-detection optical module adapted to the DWDM hollow-core optical fiber interconnect system. The laser uses an Integrated Tunable Laser Assembly (ITLA) to increase the maintainability of the optical module. Simultaneously, by externalizing the ITLA laser with TEC functionality, the temperature drift of the laser and the power consumption of the optical module are reduced, increasing the wavelength tunability of a single optical module.

[0025] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Figure 2 This is a schematic diagram of a direct-modulation, direct-detection optical transmission system provided in an embodiment of the present invention, as shown below. Figure 2 As shown, the direct-modulation, direct-detection optical transmission system includes: Multiple direct-modulation and direct-detection optical modules 1, each of which is used to generate a C-band or L-band modulated optical signal; An external multiplexer (MUX) is connected to the output of multiple direct-modulation and direct-detection optical modules 1 and is used to combine the modulated optical signals of different wavelengths output by multiple direct-modulation and direct-detection optical modules 1 into a single multiplexed optical signal. Hollow-core optical fiber 4 is connected to the output end of external multiplexer 3 and is used to transmit multiplexed optical signals; An external demultiplexer 5 (DeMUX) is connected to the output end of the hollow fiber 4 and is used to separate the multiplexed optical signal into modulated optical signals of different wavelengths and output them to the corresponding direct-modulation and direct-detection optical modules 1.

[0026] Specifically, the number of direct-modulation direct-detection optical modules 1 is not limited and is determined according to the actual situation. Each of the multiple direct-modulation direct-detection optical modules 1 is used to generate a C-band or L-band modulated optical signal. To fully utilize the abundant wavelength resources of the C-band and L-band and further expand the transmission capacity of a single fiber, the wavelengths of the multiple direct-modulation direct-detection optical modules 1 cover the entire C-band and L-band. Each direct-modulation direct-detection optical module 1 operates independently, outputting a modulated optical signal of a specific wavelength, and the output wavelengths of the multiple direct-modulation direct-detection optical modules 1 are different from each other. The modulated optical signals output by each direct-modulation direct-detection optical module 1 are sent to the respective input ports of the external multiplexer 3 via optical fibers. By using multiple direct-modulation direct-detection optical modules 1, the number of channels in the system can be flexibly expanded according to actual needs.

[0027] In some embodiments, each direct-modulation and direct-detection optical module 1 includes a digital signal processor (DSP), a driver, a modulator, a photodiode (PD), and a trans-impedance amplifier (TIA), such as... Figure 3 As shown, Figure 3 This is a structural diagram of an external direct-modulation and direct-detection optical module for C and L band ITLA provided in an embodiment of the present invention.

[0028] The externally input electrical signal is processed by the digital signal processor and then sent to the driver for amplification. The amplified electrical signal drives the modulator to generate a modulated optical signal. The modulated optical signal from the external splitter 5 is converted into an electrical signal by a photodetector, and then amplified by a transimpedance amplifier before being sent to a digital signal processor for output to an external device.

[0029] Specifically, the digital signal processor (DSP) receives externally input electrical signals and performs digital signal processing. The externally input electrical signal first enters the DSP, and after digital signal processing, is sent to the driver. The driver is connected to the output of the DSP and amplifies the electrical signal. The driver amplifies the electrical signal output by the DSP to a voltage amplitude sufficient to drive the modulator. The modulator is connected to the output of the driver and generates a C-band or L-band modulated optical signal based on the amplified electrical signal. The amplified electrical signal drives the modulator to load the electrical signal onto an optical carrier, forming a modulated optical signal carrying modulation information. The photodetector converts the modulated optical signal from the external demultiplexer 5 into an electrical signal. The transimpedance amplifier is connected to the output of the photodetector and amplifies the weak current signal output by the photodetector into a voltage signal, which is then sent to the DSP. The modulated optical signal from the external demultiplexer 5 is converted into an electrical signal by the photodetector, amplified by the transimpedance amplifier, and then sent to the DSP. The DSP recovers the signal and outputs it to an external device.

[0030] To achieve high-speed modulation in the C-band and L-band, in some embodiments, the modulator is a Mach-Zehnder modulator (MZM), and a continuous wave (CW) laser is also externally mounted on the direct-modulation and direct-detection optical module 1. The CW laser provides a continuous wave optical carrier to the Mach-Zehnder modulator; the CW laser employs an integrated tunable laser assembly.

[0031] Specifically, Mach-Zehnder modulators have the advantages of high modulation rate, low chirp, and wide operating wavelength range, making them suitable for high-speed optical modulation in the C-band and L-band. A Mach-Zehnder modulator receives an amplified electrical signal from a driver and a continuous-wave optical carrier from an external continuous-wave laser. It changes the intensity or phase of the optical carrier according to changes in the electrical signal, thereby generating a C-band or L-band modulated optical signal carrying modulation information.

[0032] An external continuous-wave laser is also provided on the direct-modulation and direct-detection optical module 1 to provide a continuous-wave optical carrier to the Mach-Zehnder modulator. The continuous-wave laser generates a stable continuous-wave laser, which is input from the outside to the Mach-Zehnder modulator inside the direct-modulation and direct-detection optical module 1 through an optical fiber.

[0033] The continuous-wave laser employs an integrated tunable laser assembly. An integrated tunable laser assembly is a modular device that integrates a tunable laser and a wavelength control unit. Its output wavelength is tunable within the C-band and L-band, allowing signals from any channel to be modulated to any wavelength. This enables a single direct-modulation and direct-detection optical module 1 to operate at any wavelength within the C-band and L-band. Simultaneously, the continuous-wave laser is configured into a tunable laser array 6, externally mounted on the direct-modulation and direct-detection optical module 1. Figure 1 The direct-modulation and direct-detection optical module 1 (with a built-in laser) avoids the impact of laser heat on other internal components, while also reducing power consumption and cost, and facilitating future maintenance and replacement. The modulated optical signal generated after modulation by the Mach-Zehnder modulator is output to the external multiplexer 3 through the modulation signal output interface.

[0034] To meet the wavelength stability requirements of dense wavelength division multiplexing (DWDM) systems, in some embodiments, such as Figure 3 As shown, the integrated tunable laser assembly is equipped with a thermoelectric cooler 7, which is used to control the temperature drift of the continuous wave laser.

[0035] Specifically, the thermoelectric cooler 7 precisely controls the operating temperature of the continuous wave laser through a closed-loop temperature control circuit, ensuring that the output wavelength of the laser does not drift with changes in ambient temperature. This strictly controls the temperature drift of the continuous wave laser, ensuring that the spacing between adjacent wavelengths meets the small spacing requirements of dense wavelength division multiplexing systems, and preventing overlapping or crosstalk between adjacent wavelength signals due to wavelength drift. Moreover, since the integrated tunable laser component is externally mounted on the direct-modulation and direct-detection optical module 1, the thermoelectric cooler 7 is also externally mounted, so the thermoelectric cooler 7 does not increase the power consumption of the optical module.

[0036] The direct-modulation direct-detection optical module 1 is equipped with a laser input interface, a modulation signal output interface, and a receiving optical signal input interface. Since the external laser increases the number of external interfaces of the direct-modulation direct-detection optical module 1, in order to achieve a higher port density within the limited space of the optical module panel, in some embodiments, the laser input interface, modulation signal output interface, and receiving optical signal input interface all adopt a multi-fiber push-on (MPO) interface.

[0037] The laser input interface is used to connect an external integrated tunable laser component to receive an externally input continuous wave optical carrier; the modulation signal output interface is used to connect an external combiner 3 to output the modulated optical signal to the external combiner 3; and the optical signal receiving input interface is used to connect an external splitter 5 to receive the modulated optical signal from the external splitter 5.

[0038] All three interfaces mentioned above use MPO interfaces, which are multi-core fiber optic connectors. Multiple fibers can be integrated into a single MPO interface, and all fibers can be connected with a single push-pull operation. By using MPO interfaces, the area occupied by the three interfaces on the optical module panel is significantly smaller than that of three independent single-core fiber optic interfaces, achieving higher port density within a limited panel space.

[0039] Since dense wavelength division multiplexing (DWDM) systems employ multiple directly modulated and directly detected optical modules 1 operating simultaneously, there is a need for mutual substitution between different optical modules. To improve system flexibility and maintainability, in some embodiments, an integrated tunable laser assembly is used, allowing the wavelength to be tunable across the entire C-band and L-band. This enables a single directly modulated and directly detected optical module 1 to cover any wavelength in both the C-band and L-band. By employing an integrated tunable laser assembly with tunable wavelengths across the entire C-band and L-band, a single directly modulated and directly detected optical module 1 can cover any wavelength in both the C-band and L-band, providing wavelength tunability and reducing the operational complexity of the laser and optical modules.

[0040] Besides the modulation method described above, which uses a Mach-Zehnder modulator in conjunction with an external continuous-wave laser, some embodiments use a directly modulated laser (DML) or an electro-absorption modulated laser (EML). The externally input electrical signal is amplified by a driver and directly drives the DML or EML to generate a modulated optical signal. In this embodiment, both the DML and EML operate in the C-band or L-band. Because the DML and EML integrate the light source and modulation function, their structures are more compact.

[0041] An external multiplexer 3 is connected to the output of multiple direct-modulation and direct-detection optical modules 1. The external multiplexer 3 combines the modulated optical signals of different wavelengths output from the multiple direct-modulation and direct-detection optical modules 1 into a single multiplexed optical signal. The external multiplexer 3 has multiple input ports, each of which is connected to the modulation signal output interface of the multiple direct-modulation and direct-detection optical modules 1.

[0042] Traditional silica optical fiber, due to its high dispersion, cannot support C-band and L-band DWDM direct-mode and direct-detection systems. Hollow-core optical fiber 4 exhibits lower attenuation coefficients in the C-band and L-band than traditional silica optical fiber, while its dispersion coefficient is less than 1 / 6 that of traditional silica optical fiber in the C-band and L-band, and its nonlinear coefficient is also significantly lower. Therefore, in this embodiment, hollow-core optical fiber 4 is connected to the output of the external multiplexer 3 for transmitting multiplexed optical signals. Hollow-core optical fiber 4 enables long-distance, high-quality signal transmission of the direct-mode and direct-detection optical module 1 in the C-band and L-band without causing severe power attenuation at the receiving end due to excessive dispersion.

[0043] To improve the power of the received optical signal, in some embodiments, an erbium-doped fiber amplifier (EDFA) is also provided in the transmission link of the hollow fiber 4. The erbium-doped fiber amplifier is used to amplify the power of the multiplexed optical signal.

[0044] Specifically, the erbium-doped fiber amplifier uses erbium-doped fiber as the gain medium to amplify C-band and L-band optical signals under the excitation of pump light. In practical applications, depending on the specific system transmission scenario, an erbium-doped fiber amplifier can be selectively added to the transmission link of hollow fiber 4 to compensate for the insertion loss and transmission loss introduced by the multiplexer 3, demultiplexer 5, and hollow fiber 4, thereby increasing the power of the received optical signal and extending the transmission distance of the system.

[0045] An external wavelength divider 5 is connected to the output end of the hollow fiber 4. It separates the transmitted multiplexed optical signal into modulated optical signals of different wavelengths and outputs them to the corresponding direct-modulation-direct-detection optical modules 1. In other words, the separated modulated optical signals of different wavelengths are transmitted to the receiving end of the corresponding direct-modulation-direct-detection optical module 1. The external wavelength divider 5 corresponds to the wavelength of the external multiplexer 3, with each output port corresponding to a specific wavelength. These output ports are connected to the receiving end of the corresponding direct-modulation-direct-detection optical module 1 via optical fibers. Each direct-modulation-direct-detection optical module 1 converts the received modulated optical signal into an electrical signal and outputs it to an external device.

[0046] As described above, the direct-modulation and direct-detection optical transmission system provided by this invention specifically comprises an external ITLA direct-modulation and direct-detection optical module 1 covering C-band and L-band, and a DWDM optical interconnect system. To enable those skilled in the art to better understand the system provided by this invention, the solution of this invention will be described again below.

[0047] Since a single optical module supports a limited number of channels, multiple optical modules are used to increase the number of channels in the system until the entire C and L bands are covered. The combined signals are then sent into the optical fiber for transmission via an external multiplexer 3. At the receiving end, the signals are split by a demultiplexer 5 and sent to the receiving end of the direct-modulation direct-detection optical module 1 to complete signal reception. Additionally, depending on the specific system transmission scenario, an EDFA can be added to the optical fiber link to increase the power of the received optical signal. Optical signal modulation is achieved using a CW laser and an MZM modulator, with the CW laser employing an ITLA. The operating wavelengths of the laser, modulator, and PD are all changed to the C and L bands. Furthermore, the external ITLA requires the addition of a TEC temperature control module to strictly control the laser's temperature drift, thereby reducing the spacing between adjacent wavelengths and supporting DWDM optical system transmission. The number of channels can be selected from 1 to the full-wavelength number of C and L band channels. The optical module's inputs and outputs include a laser input interface, a modulation signal output interface, and a received optical signal input interface, adding a laser input interface compared to the original optical module. All interfaces can be configured with MPO to increase port density.

[0048] Compared to traditional CWDM quartz fiber optical transmission systems, the direct-modulation direct-detection optical transmission system provided by this invention requires adjustments to the original direct-modulation direct-detection transmission system architecture and optical module structure. First, it breaks through the original transmission system architecture where one direct-modulation direct-detection optical module 1 occupies one optical fiber. An external DWDM multiplexer 3 is used to combine the output wavelengths of multiple direct-modulation direct-detection optical modules 1 before transmitting them into a hollow-core optical fiber 4. At the receiving end, a demultiplexer 5 separates the wavelength signals of each optical module before sending them to the corresponding optical module for reception, ultimately achieving a DWDM optical transmission system covering the entire C-band and L-band. Second, to realize this DWDM hollow-core optical transmission system, the operating wavelength of the original direct-modulation direct-detection optical module 1 needs to be adjusted from the O-band to the C-band and L-band. Third, the interval between different wavelength signals in the DWDM system is very small, requiring the addition of TEC functionality to the laser to control its temperature drift. However, adding a TEC (Transmission Controlled Energy) increases the overall power consumption of the optical module. Therefore, further externalizing the laser to form a laser array avoids the increased power consumption of the optical module due to the TEC. Furthermore, since DWDM systems use multiple optical modules operating simultaneously, there is a need for different optical modules to be interchangeable. Therefore, ITLA (Inter-Independent Laser Interface) can be used to achieve wavelength tunability for different optical modules, improving the maintainability of the laser and enhancing system flexibility. Externalizing the laser increases the number of external interfaces on the optical module; MPO (Multi-Port Optical) interfaces can be used to increase the wavelength port density of a single optical module.

[0049] This invention significantly improves the transmission capacity of a single fiber. At the same time, based on the new transmission system architecture, the structure of the IMDD optical module has been redesigned, maintaining the advantages of the IMDD optical module in terms of cost, power consumption and latency. It can be widely used in high-capacity, low-latency and low-cost optical interconnection scenarios between data centers.

[0050] The above describes a direct-modulation, direct-detection optical transmission method. This embodiment also provides a direct-modulation, direct-detection optical transmission method applied to the above-described direct-modulation, direct-detection optical transmission system. Figure 4 A flowchart of a direct-modulation, direct-detection optical transmission method provided in an embodiment of the present invention is shown below. Figure 4 As shown, the method includes: S10: Utilizes multiple direct-modulation and direct-detection optical modules to generate modulated optical signals of different wavelengths in the C-band or L-band respectively; S11: Combines modulated optical signals of different wavelengths output from multiple direct-modulation and direct-detection optical modules into a single multiplexed optical signal using an external multiplexer; S12: Transmit the multiplexed optical signal through a hollow optical fiber; S13: The multiplexed optical signal transmitted through hollow optical fiber is separated into modulated optical signals of different wavelengths by an external wavelength divider, and then output to the corresponding direct-modulation and direct-detection optical modules for reception.

[0051] The direct-modulation and direct-detection optical transmission method provided in this embodiment has the same or corresponding technical features as the direct-modulation and direct-detection optical transmission system described above, and the effect is the same.

[0052] The foregoing has provided a detailed description of a direct-modulation, direct-detection optical transmission system and optical transmission method provided by the present invention. The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the systems disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the system section description. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the present invention.

[0053] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

Claims

1. A direct-modulation, direct-detection optical transmission system, characterized in that, include: Multiple direct-modulation and direct-detection optical modules, each of which is used to generate a C-band or L-band modulated optical signal; An external multiplexer is connected to the output of the multiple direct-modulation and direct-detection optical modules to combine the modulated optical signals of different wavelengths output by the multiple direct-modulation and direct-detection optical modules into a single multiplexed optical signal. A hollow optical fiber is connected to the output end of the external multiplexer to transmit the multiplexed optical signal; An external wavelength division multiplexer is connected to the output end of the hollow optical fiber to separate the multiplexed optical signal into modulated optical signals of different wavelengths and output them to the corresponding direct-modulation and direct-detection optical modules.

2. The direct-modulation, direct-detection optical transmission system according to claim 1, characterized in that, The wavelengths of the multiple direct-modulation and direct-detection optical modules cover the entire C-band and L-band.

3. The direct-modulation, direct-detection optical transmission system according to claim 1 or 2, characterized in that, Each of the direct-modulation and direct-detection optical modules includes a digital signal processor, a driver, a modulator, a photodetector, and a transimpedance amplifier; The externally input electrical signal is processed by the digital signal processor and then sent to the driver for amplification. The amplified electrical signal drives the modulator to generate the modulated optical signal. The modulated optical signal from the external wavelength divider is converted into an electrical signal by the photodetector, amplified by the transimpedance amplifier, and then sent to the digital signal processor for output to an external device.

4. The direct-modulation, direct-detection optical transmission system according to claim 3, characterized in that, The modulator is a Mach-Zehnder modulator, and a continuous wave laser is also provided outside the direct modulation and direct detection optical module to provide a continuous wave optical carrier to the Mach-Zehnder modulator. The continuous wave laser employs an integrated tunable laser assembly.

5. The direct-modulation, direct-detection optical transmission system according to claim 4, characterized in that, The integrated tunable laser assembly is equipped with a thermoelectric cooler for controlling the temperature drift of the continuous wave laser.

6. The direct-modulation, direct-detection optical transmission system according to claim 3, characterized in that, The direct-modulation and direct-detection optical module is equipped with a laser input interface, a modulation signal output interface, and a receiving optical signal input interface. The laser input interface, modulation signal output interface, and receiving optical signal input interface all adopt multi-core push-pull interfaces.

7. The direct-modulation, direct-detection optical transmission system according to claim 1, characterized in that, The transmission link of the hollow optical fiber is also equipped with an erbium-doped fiber amplifier, which is used to amplify the power of the multiplexed optical signal.

8. The direct-modulation, direct-detection optical transmission system according to claim 4, characterized in that, The integrated tunable laser assembly has a wavelength that is adjustable throughout the C-band and L-band, so that a single direct-modulation and direct-detection optical module can cover any wavelength in the C-band and L-band.

9. The direct-modulation, direct-detection optical transmission system according to claim 3, characterized in that, The modulator is a direct-modulated laser or an electro-absorption modulated laser. The externally input electrical signal is amplified by the driver and directly drives the direct modulation laser or the electroabsorption modulation laser to generate the modulation optical signal.

10. A direct-modulation, direct-detection optical transmission method, characterized in that, The method, applied to the direct-modulation and direct-detection optical transmission system according to any one of claims 1 to 9, comprises: Multiple direct-modulation and direct-detection optical modules are used to generate modulated optical signals of different wavelengths in the C-band or L-band respectively; The modulated optical signals of different wavelengths output from the multiple direct-modulation and direct-detection optical modules are combined into a single multiplexed optical signal by an external multiplexer. The multiplexed optical signal is transmitted through a hollow optical fiber; The multiplexed optical signal transmitted through hollow optical fiber is separated into modulated optical signals of different wavelengths by an external wavelength divider, and then output to the corresponding direct-modulation and direct-detection optical modules for reception.

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