A DWDM ROF module with OTDR function

Abstract

This invention relates to a DWDM ROF module with OTDR functionality. It mainly includes a TOSA, ROSA, FPGA, DRIVER, and OTDR. The TOSA uses an external MUX to combine different wavelengths, and one channel's transmit optical path has an optical circulator for OTDR detection, monitoring the fiber optic link status. The ROSA has a built-in DEMUX for wavelength division. The FPGA provides control signals to the entire module, including controlling the DRIVER's registers and reporting information, providing external communication interfaces, monitoring the optical power at the receiving end, and generating pulsed electrical signals and analyzing the OTDR's reflected signals. The DRIVER controls the laser's optical power, implementing APC functionality, and monitors the laser's overall operating status. In terms of OTDR functionality, it controls the laser's pulsed optical signal emission. This invention features minimal hardware, low cost, comprehensive functionality, high performance, and strong compatibility, meeting the data transmission needs of macro base stations, fiber optic detection requirements, and reducing the cost of remote site deployment.

Description

Technical Field

[0001] This invention relates to the field of optical transmission technology, and in particular to a DWDM ROF module with OTDR function, mainly used for optical transmission in outdoor macro stations to solve problems such as rate, distance, compatibility, and power consumption, while also solving the problem of monitoring optical fiber links. Background Technology

[0002] Currently, mainstream macro base station solutions are based on digital optical modules with speeds of 25G / bps or 10G / bps. However, the maximum speed of digital optical modules is constant, requiring frequency conversion on the AAU (Active Antenna Unit) side. Data compression and processing are also necessary before optical transmission, resulting in complex digital signal processing on the AAU side, high power consumption, and high overall maintenance and management costs. Furthermore, speed upgrades require replacing the optical modules with higher-speed ones. Routine maintenance also necessitates monitoring the fiber optic link's condition. Existing digital optical module solutions cannot meet the ever-increasing demands.

[0003] In view of the above, how to overcome the shortcomings of existing technologies and meet the current and future needs of outdoor macro base station optical transmission is a problem to be solved in this technical field. Summary of the Invention

[0004] To address the aforementioned shortcomings or improvement needs of existing technologies, this invention provides a DWDM (Dense Wavelength Division Multiplexing) ROF (Radio Frequency Onboard Array) module with OTDR (Optical Time Domain Reflectometer) functionality. Utilizing ROF technology, it can directly transmit radio frequency signals, reducing the overall complexity of the AAU (Analog Access Array) side, minimizing digital signal processing, and placing all signal processing on the BBU (Building Baseband Unit) side. This facilitates front-end deployment, reduces power consumption, and increases reliability. Processing digital signals in the equipment room provides a better overall environment, simplifying management and maintenance. Furthermore, ROF technology is compatible with different frequencies and data rates, with the rate primarily determined by signal bandwidth and modulation scheme. Multiplexed wavelength division multiplexing effectively saves fiber optic resources, and combined with frequency division multiplexing, it can transmit multiple signals, meeting the data transmission requirements of macro base stations. Additionally, the OTDR function can meet the status monitoring needs of the fiber optic link, and the reuse of one laser can reduce overall costs.

[0005] The embodiments of the present invention adopt the following technical solutions:

[0006] This invention provides a DWDM ROF module with OTDR functionality, including TOSA, ROSA, FPGA, DRIVER, and OTDR, specifically:

[0007] The TOSA uses an external MUX to combine different wavelengths, and one of the channels has an optical circulator in its transmission path for OTDR detection to check the status of the fiber optic link.

[0008] The ROSA has a built-in DEMUX for wavelength division;

[0009] The FPGA provides control signals to the entire module, including controlling the DRIVER's registers and reporting information, providing external communication interfaces, monitoring the optical power of the receiver, and generating pulse electrical signals and analyzing and processing the reflected signals of the OTDR.

[0010] The driver is used to control the optical power of the laser, realize the APC function, monitor the working status of the entire laser, and control the laser to emit pulsed light signals in the OTDR function.

[0011] Furthermore, at the transmitting end, the radio frequency signal is accessed through the radio frequency interface, and the radio frequency signal is modulated onto lasers of different wavelengths by the modulator. Then, multiple wavelengths of light are combined into one optical fiber through an external MUX combiner and transmitted out. In order to offset the impact of the MUX on performance, an optical amplifier is also set after the optical fiber to amplify the optical signals of different wavelengths of DWDM.

[0012] Furthermore, at the receiving end, the multi-wavelength ROSA device demultiplexes the received optical signal into optical signals of different wavelengths and sends them to multiple detectors. The detectors convert the optical signals into electrical signals, which are then amplified by an LNA to restore the signal from the transmitting end.

[0013] Furthermore, one output optical power of the optical circulator and the optical signal returned by the return optical fiber are used for OTDR detection.

[0014] Furthermore, the OTDR link includes an optical detection unit, an ADC, and a clock, wherein:

[0015] The optical detection unit is connected to the optical circulator and the ADC. The optical detection unit is used to convert optical signals into voltage signals and includes a photodetector and a weak signal amplification circuit.

[0016] The ADC is connected to the optical detection unit and the FPGA, and is used to sample electrical signals;

[0017] The clock is connected to the ADC and the FPGA. The clock is a sine wave signal generated by a temperature-compensated crystal oscillator or a temperature-controlled crystal oscillator, with a frequency of 10MHz or 100MHz.

[0018] Furthermore, a TEC is provided at the bottom of the laser, and the laser temperature is controlled by the TEC chip to meet the operating temperature requirements of the macro station.

[0019] Furthermore, it also includes a power supply circuit, which supplies power to different functional modules of the entire module, and the power supply circuit is an LDO converter power supply method.

[0020] Furthermore, it also includes a matching circuit for achieving a 50Ω match between the laser or detector.

[0021] Furthermore, it also includes a storage unit, which contains DDR and flash memory. The DDR is used for data storage during data processing, and the flash memory is used to store the application programs of the module.

[0022] Furthermore, the entire module's RF traces are 50Ω matched to microstrip lines.

[0023] Compared with existing technologies, the beneficial effects of this invention are as follows: it can effectively solve the problem of multi-channel data transmission in macro stations; compared with digital solutions, it can reduce the complexity and cost of the entire system and reduce the dependence on digital chips; at the same time, it has the function of OTDR, which can directly detect the status of the entire optical fiber link; it adopts the multiplexing of optical devices and chips, which effectively reduces costs; and it adopts DWDM wavelength division multiplexing, which can save optical fiber resources and reduce back-end costs.

[0024] The DWDM ROF module with OTDR function of the present invention requires less additional hardware, has low cost, comprehensive functions, good performance, high fiber optic resource utilization, and strong compatibility, so as to meet the data transmission needs of macro stations, fiber optic detection needs, and reduce the cost of remote site deployment. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0026] Figure 1 This is a schematic diagram of a single-channel function module of a DWDM ROF module with OTDR function provided in Embodiment 1 of the present invention;

[0027] Figure 2This is a schematic diagram illustrating the interaction between two DWDM ROF modules with OTDR functionality provided in Embodiment 1 of the present invention.

[0028] Figure 3 This is a schematic diagram of an OTDR link provided in Embodiment 1 of the present invention. Detailed Implementation

[0029] 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.

[0030] Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] Example 1:

[0032] like Figure 1 As shown, for reference Figure 2 , Figure 3 Embodiment 1 of the present invention provides a DWDM ROF module with OTDR function, including TOSA (Transmitter Optical Subassembly), ROSA (Receiver Optical Subassembly), FPGA (Field-Programmable Gate Array), DRIVER (laser driver chip) and OTDR. The TOSA uses an external MUX (multiplexer) to combine different wavelengths, and one of its transmission optical paths has an optical circulator for OTDR detection, monitoring the fiber optic link status. The ROSA has a built-in DEMUX (demultiplexer) for wavelength division. The FPGA provides control signals to the entire module, including controlling the driver's registers and reporting information, providing external communication interfaces, monitoring the optical power at the receiving end, generating pulsed electrical signals for the OTDR, and analyzing and processing the reflected signals from the OTDR. The driver controls the laser's optical power, implementing the APC (Automatic Power Control) function, and monitors the overall laser's operating status. In terms of OTDR functionality, it controls the laser to emit pulsed optical signals.

[0033] In this preferred embodiment, the solution employs low-cost direct modulation, i.e., optical amplitude modulation, which can meet the requirements of low cost, high performance, and high volume for SUB 6 applications. This module can effectively reduce the complexity of the entire communication system, and by adjusting the bandwidth and modulation method, it can be compatible with different data rates. Furthermore, the core chip can be domestically produced, effectively solving problems related to transmission rate, power consumption, compatibility, performance, and supply chain.

[0034] refer to Figure 1 , Figure 2 The working process of this preferred embodiment is as follows:

[0035] At the transmitting end, the radio frequency signal is received through the radio frequency interface. The modulator modulates the radio frequency signal onto lasers of different wavelengths. Then, the multiple wavelengths of light are combined into one optical fiber through an external MUX combiner and transmitted out. In order to offset the impact of the MUX on performance, an optical amplifier is also set after the optical fiber to amplify the optical signals of different wavelengths of DWDM.

[0036] At the receiving end, the multi-wavelength ROSA device demultiplexes the received optical signal into optical signals of different wavelengths and sends them to multiple detectors. The detectors convert the optical signals into electrical signals, which are then amplified by an LNA (Low Noise Amplifier) ​​to restore the signal from the transmitting end.

[0037] This preferred embodiment employs a separate TOSA and ROSA structure for the optical device. The TOSA uses an external MUX for wavelength multiplexing, while the ROSA uses a built-in DEMUX for wavelength splitting. Channel 1's transmit optical path includes an optical circulator for OTDR detection, monitoring the fiber optic link status. Specifically, the TOSA in this embodiment consists of multiple single-wavelength BOX / TO packaged TOSA optical devices, primarily containing a laser, a TEC (Thermo Electric Cooler), and some optical components for transmitting optical signals and controlling the laser chip temperature. The ROSA device in this embodiment is a multi-wavelength BOX packaged ROSA optical device, primarily containing a detector and some optical components for receiving optical signals. Optical amplifiers, including but not limited to EDFA (Erbium Doped Fiber Amplifier), SOA (Semiconductor Optical Amplifier), and OFA (Optical Fiber Amplifier), are located between the MUX and the ROSA device.

[0038] In this preferred embodiment, the laser has a TEC (Transducer Temperature Controller) at its bottom. The TEC chip controls the laser temperature to meet the macrostation's operating temperature requirements, ensuring stable laser performance within the operating temperature range. The TEC circuit in this embodiment primarily controls the Peltier diode at the bottom of the laser, controlling cooling or heating to ensure the laser meets the operating temperature requirements. Furthermore, the main laser type in this embodiment is a DFB (Distributed Feed Back) laser, and the detector type is a PD (Photo-Diode).

[0039] In this preferred embodiment, the FPGA is the main controller. The FPGA module provides control signals to the entire module, including controlling the registers of the driver and reporting information. The external communication interface is either I2C or SPI (Serial Peripheral Interface). The FPGA is mainly used to monitor the status of the ambient temperature, laser, optical path, power supply, etc., adjust parameters such as the optical power of the laser, monitor the optical power of the receiver, generate pulse electrical signals and control and analyze the entire OTDR link, analyze and process the reflected signals of the OTDR, and also for alarm protection functions.

[0040] This preferred embodiment also includes a power supply circuit. This power supply circuit supplies power to different functional modules of the entire module. The power supply circuit uses an LDO (Low Dropout Regulator) voltage converter to provide a low-ripple and low-noise regulated power supply to the entire module. The main power supplies are +3.3V, +5V, and +6V.

[0041] In this preferred embodiment, the driver drives and monitors the entire laser, primarily providing current to drive the laser, controlling the optical power, and also controlling the emission of pulsed optical signals in the OTDR.

[0042] This preferred embodiment includes a T-BIAS (T-type bias) circuit, which mainly modulates the radio frequency signal onto the laser. The LNA in this preferred embodiment primarily amplifies the energy of the received weak signal.

[0043] In this preferred embodiment, the optical circulator outputs optical power on one path and returns optical signal via another optical fiber, which is used for OTDR detection.

[0044] refer to Figure 3In this preferred embodiment, the OTDR link includes an optical detection unit, an ADC (Analog-to-Digital Converter), and a clock. The optical detection unit is connected to the optical circulator and the ADC, and is used to convert optical signals into voltage signals. It includes a photodetector and a weak signal amplification circuit. The ADC is connected to the optical detection unit and the FPGA, and is mainly used to sample electrical signals. The clock is connected to the ADC and the FPGA. The clock is a sine wave signal generated by a temperature-compensated crystal oscillator or a temperature-controlled crystal oscillator, with a frequency of 10MHz or 100MHz.

[0045] In this preferred embodiment, a matching circuit is also included to achieve 50Ω matching for the laser or detector. In this embodiment, the entire module's RF traces are microstrip lines with 50Ω matching.

[0046] In this preferred embodiment, a storage unit is also included, which mainly stores FPGA-related data. The storage unit includes DDR and flash memory. The DDR is used for data storage during data processing, and the flash memory is used for storing the application program of the module.

[0047] In the above technical solution of this embodiment, the use of ROF technology can directly transmit radio frequency signals, reducing the overall complexity of the AAU side, reducing digital signal processing, and placing all signal processing on the BBU side, which facilitates front-end deployment, reduces power consumption, and increases reliability. Processing digital signals in the equipment room provides a better overall environment and facilitates management and maintenance. Simultaneously, ROF technology is compatible with different frequencies and rates, with the rate mainly determined by signal bandwidth and modulation method. Multiplexed wavelength division multiplexing can effectively save fiber optic resources, and combined with frequency division multiplexing, multiple signals can be transmitted to meet the data transmission requirements of macro base stations. Furthermore, the OTDR function can meet the status monitoring of fiber optic links, and multiplexing one of the lasers can reduce overall costs.

[0048] In summary, this invention can effectively solve the problem of multi-channel data transmission in macro stations. Compared with digital solutions, it can reduce the complexity and cost of the entire system, reduce the dependence on digital chips, and has OTDR functionality to directly detect the status of the entire fiber optic link. The reuse of optical devices and chips effectively reduces costs, and the use of DWDM wavelength division multiplexing can save fiber optic resources and reduce backend costs.

[0049] The DWDM ROF module with OTDR function of the present invention requires less additional hardware, has low cost, comprehensive functions, good performance, high fiber optic resource utilization, and strong compatibility, so as to meet the data transmission needs of macro stations, fiber optic detection needs, and reduce the cost of remote site deployment.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A DWDM ROF module with OTDR function, characterized in that, Deployed on the AAU side, including TOSA, ROSA, FPGA, DRIVER, and OTDR, specifically: The TOSA uses an external MUX to combine different wavelengths, and one of the channels has an optical circulator in its transmission path for OTDR detection to check the status of the fiber optic link. The ROSA has a built-in DEMUX for wavelength division; The FPGA provides control signals to the entire module, including controlling the registers of the driver and reporting information, providing an external communication interface, and monitoring the optical power of the receiver. At the same time, the FPGA generates pulse electrical signals and analyzes and processes the reflected signals of the OTDR. The DRIVER is used to control the optical power of the laser, realize the APC function, and monitor the working status of the entire laser. In terms of OTDR function, it controls the laser to emit pulsed light signals. At the transmitting end, the radio frequency signal is input through the radio frequency interface, and the radio frequency signal is modulated onto lasers of different wavelengths by the modulator. The multiple wavelengths of light are combined into one optical fiber through the external MUX combiner and transmitted out. In order to offset the impact of the MUX on performance, an optical amplifier is also set after the optical fiber to amplify the optical signals of different wavelengths of DWDM. The OTDR link includes an optical detection unit, an ADC, and a clock. The optical detection unit is connected to the optical circulator and the ADC. The optical detection unit includes a photodetector and a weak signal amplification circuit, which is used to convert the optical signal into a voltage signal. The ADC is connected to the optical detection unit and the FPGA, and is used to sample the electrical signal. The clock is connected to the ADC and the FPGA. The clock is a sine wave signal generated by a temperature-compensated crystal oscillator or a temperature-controlled crystal oscillator.

2. The DWDM ROF module with OTDR function according to claim 1, characterized in that, At the receiving end, the multi-wavelength ROSA device demultiplexes the received optical signal into optical signals of different wavelengths and sends them to multiple detectors. The detectors convert the optical signals into electrical signals, which are then amplified by an LNA to restore the signal from the transmitting end.

3. The DWDM ROF module with OTDR function according to claim 1, characterized in that, One output optical power of the optical circulator and the other return optical signal are used for OTDR detection.

4. The DWDM ROF module with OTDR function according to claim 1, characterized in that, The clock frequency is 10MHz or 100MHz.

5. The DWDM ROF module with OTDR function according to claim 1, characterized in that, The laser is equipped with a TEC at its bottom, and the laser temperature is controlled by the TEC chip to meet the operating temperature requirements of the macro station.

6. The DWDM ROF module with OTDR function according to claim 1, characterized in that, It also includes a power supply circuit, which supplies power to different functional modules of the entire module. The power supply circuit is an LDO converter power supply method.

7. The DWDM ROF module with OTDR function according to claim 1, characterized in that, It also includes a matching circuit for achieving a 50Ω match between the laser or detector.

8. The DWDM ROF module with OTDR function according to claim 1, characterized in that, It also includes a storage unit, which contains DDR and flash memory. The DDR is used for data storage during data processing, and the flash memory is used to store the application programs of the module.

9. The DWDM ROF module with OTDR function according to any one of claims 1-8, characterized in that, The entire module's RF traces are microstrip line 50Ω matched.

Images