An optical modulation degree stabilizing system of a tunable DWDM wavelength RFoG optical node

Abstract

The application discloses an optical modulation degree stabilizing system of a tunable DWDM wavelength RFoG optical node, which comprises an uplink signal attenuation circuit, an uplink signal amplification circuit, a tunable laser, an optical power and radio frequency level sampling circuit, an optical power control circuit and a microprocessor circuit; the output end of the uplink signal attenuation circuit is connected with the input end of the uplink signal amplification circuit; the output end of the uplink signal amplification circuit is connected with the input end of the tunable laser; the output end of the tunable laser is connected with the input end of the optical power and radio frequency level sampling circuit; the output end of the optical power and radio frequency level sampling circuit is connected with the input end of the microprocessor circuit; the output end of the microprocessor circuit is respectively connected with the input end of the optical power control circuit and the input end of the uplink signal attenuation circuit; and the output end of the optical power control circuit is connected with the input end of the tunable laser.

Description

Technical Field

[0001] This invention relates to the field of cable television technology, and in particular to a system for stabilizing the optical modulation of a tunable DWDM wavelength RFoG optical node. Background Technology

[0002] Tunable DWDM wavelength RFoG optical nodes employing dense wavelength division multiplexing (DWDM) technology can effectively eliminate optical beat frequency interference and are increasingly used in cable television networks. However, due to the high cost of butterfly-packaged wavelength-tuned DFB lasers, their widespread use in access networks is limited. Currently, coaxial TOSA lasers are more commonly used. However, when the same RFoG optical node operates at different DWDM wavelengths, the laser's output optical power varies significantly. For example, the maximum and minimum output optical power of an RFoG optical node operating at 16 different wavelengths can exceed 2dB, and the optical power stability exceeds ±10%. These differences in output optical power cause variations in the uplink channel's optical modulation, leading to changes in the received uplink signal level and affecting the transmission quality of the cable television network.

[0003] To address the aforementioned technical problems, this invention proposes an optical modulation stabilization system for tunable DWDM wavelength RFoG optical nodes. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a tunable DWDM wavelength RFoG optical node optical modulation stabilization system. This system improves the transmission quality of cable television networks by adding a customized heat sink to a coaxial TOSA laser with a built-in semiconductor cooler and thermistor, and by controlling the optical output power and optical modulation of the stable optical node through related control circuits and software.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An optical modulation stabilization system for a tunable DWDM wavelength RFoG optical node, the optical modulation stabilization system being installed at the user end, includes an uplink signal attenuation circuit, an uplink signal amplification circuit, a tunable laser, an optical power and RF level sampling circuit, an optical power control circuit, and a microprocessor circuit;

[0007] The output of the uplink signal attenuation circuit is connected to the input of the uplink signal amplification circuit. The output of the uplink signal amplification circuit is connected to the input of the tunable laser. The output of the tunable laser is connected to the input of the optical power and RF level sampling circuit. The output of the optical power and RF level sampling circuit is connected to the input of the microprocessor circuit. The output of the microprocessor circuit is connected to the input of the optical power control circuit and the input of the uplink signal attenuation circuit, respectively. The output of the optical power control circuit is connected to the input of the tunable laser.

[0008] The optical power and RF level sampling circuit acquires the optical power and RF level values ​​of the output optical signal of the tunable laser, adjusts the optical power and RF level values, and outputs the adjusted optical power and RF level values ​​to the microprocessor circuit. The microprocessor circuit controls the attenuation of the uplink signal attenuation circuit, thereby adjusting the RF input level of the tunable laser; on the other hand, it controls the optical power of the optical power control circuit, thereby controlling the optical power of the tunable laser, and realizing stable control of the optical modulation of the optical node.

[0009] Furthermore, the tunable laser is a TOSA laser, which is equipped with a heat sink to achieve stable output of optical signals at 16 different wavelengths within the range of 1610±3nm.

[0010] Furthermore, the chip model of the uplink signal attenuation circuit is MADP-007167-0287FT; the chip model of the uplink signal amplification circuit is AE427; and the chip model of the microprocessor circuit is STC8H3K32S2.

[0011] Furthermore, the optical power of the output optical signal of the tunable laser is expressed as:

[0012] P out =3.5397*U-0.0001

[0013] Among them, P out The output optical power of the tunable laser is represented by ; U represents the photoelectric conversion voltage value of the optical power.

[0014] Furthermore, the radio frequency level value of the output optical signal of the tunable laser is expressed as:

[0015] P = V out / 0.05-60

[0016] Where P represents the output radio frequency level of the tunable laser; V out This indicates the sampled voltage value.

[0017] Furthermore, the optical modulation scheme of the optical node is expressed as follows:

[0018]

[0019] Where OMI represents optical modulation; U represents the photoelectric conversion voltage value of optical power; and P represents the output radio frequency level value of the tunable laser.

[0020] Furthermore, the adjustment of the optical power of the tunable laser output optical signal specifically involves:

[0021] A1. Calculate the first actual optical power of the output optical signal of the tunable laser;

[0022] A2. Calculate the first deviation from the preset optical power value of the first actual optical power value and determine whether the first deviation from the preset optical power value is within ±0.05mW. If not, calculate the first optical power control value.

[0023] A3. The first optical power control value is sent to the optical power control circuit via the microprocessor circuit;

[0024] A4. Calculate the second actual optical power of the output optical signal of the tunable laser;

[0025] A5. Calculate the second deviation from the preset optical power value, and determine whether the second deviation is within ±0.02mW. If not, calculate the second optical power control value and continue to execute step A3.

[0026] Furthermore, the adjustment of the radio frequency level value of the tunable laser specifically involves:

[0027] A6. If the first deviation from the nominal value is within ±0.05mW, calculate the first actual level value of the optical signal at the location of the tunable laser, and calculate the first optical modulation index (OMI) value of the tunable laser based on the first actual level value.

[0028] A7. Calculate whether the first OMI deviation value between the first optical modulation OMI value and the preset OMI value is within ±0.5%. If yes, then end; if no, then calculate the first radio frequency level control value.

[0029] A8. The microprocessor circuit sends the first radio frequency level control value to the uplink signal attenuation circuit;

[0030] A9. Calculate the second actual level value of the output optical signal of the tunable laser, and calculate the second optical modulation index (OMI) value of the tunable laser based on the second actual level value;

[0031] A10. Calculate whether the second OMI deviation value between the second optical modulation OMI value and the preset OMI value is within ±0.3%. If not, calculate the second RF level control value and continue to execute step A8; if yes, end.

[0032] Furthermore, in step A5, it is determined whether the second deviation from the nominal value is within ±0.02mW. If so, step A6 is executed.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. The RFoG optical node with a tunable DWDM wavelength RFoG optical node optical modulation stabilization system provides an effective solution to the OBI (optical beat frequency interference) noise problem in the backhaul channel of a bidirectional HFC network.

[0035] 2. This invention significantly reduces the procurement cost of transmission equipment for cable TV operators by adding a customized heat sink to a coaxial TOSA laser with a built-in semiconductor cooler and thermistor, compared to the original butterfly-packaged wavelength-tuned DFB laser.

[0036] 3. This invention controls the optical output power and optical modulation of a stable optical node through relevant control circuits and software. A tunable DWDM wavelength optical node with stable optical modulation can improve the transmission quality of cable television networks and reduce the operation and maintenance costs of cable television operators. Attached Figure Description

[0037] Figure 1 This is a structural diagram of an optical modulation stabilization system for a tunable DWDM wavelength RFoG optical node provided in Embodiment 1;

[0038] Figure 2 This is a structural diagram of the tunable laser provided in Embodiment 1;

[0039] Figure 3 This is a schematic diagram of the heat sink structure provided in Embodiment 1;

[0040] Figure 4 This is a schematic diagram of the heat sink structure provided in Embodiment 1;

[0041] Figure 5 This is a schematic diagram of the tunable laser and heat sink structure provided in Embodiment 1;

[0042] Figure 6 This is a flowchart illustrating the adjustment of the optical power and radio frequency level of the tunable laser provided in Embodiment 2. Detailed Implementation

[0043] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0044] The purpose of this invention is to address the problem that different wavelengths of output cause changes in the optical modulation of the uplink channel, resulting in changes in the received level of the uplink signal. The invention proposes an optical modulation stabilization system for tunable DWDM wavelength RFoG optical nodes that can effectively solve the OBI (Optical Beat Interference) noise problem in the backhaul channel of bidirectional HFC networks while reducing costs.

[0045] Example 1

[0046] This embodiment provides an optical modulation stabilization system for a tunable DWDM wavelength RFoG optical node. The optical modulation stabilization system is installed at the user end, such as... Figure 1 As shown, it includes an uplink signal attenuation circuit 1, an uplink signal amplification circuit 2, a tunable laser 3, an optical power and RF level sampling circuit 4, an optical power control circuit 5, and a microprocessor circuit 6.

[0047] The input terminal of the uplink signal attenuation circuit 1 is connected to the uplink signal input terminal of the external cable television network. The output terminal of the uplink signal attenuation circuit 1 is connected to the input terminal of the uplink signal amplification circuit 2. The output terminal of the uplink signal amplification circuit 2 is connected to the input terminal of the tunable laser 3. The output terminal of the tunable laser 3 is connected to the input terminal of the optical power and radio frequency level sampling circuit 4. The output terminal of the optical power and radio frequency level sampling circuit 4 is connected to the input terminal of the microprocessor circuit 6. The output terminal of the microprocessor circuit 6 is connected to the input terminal of the optical power control circuit 5 and the input terminal of the uplink signal attenuation circuit 1, respectively. The output terminal of the optical power control circuit 5 is connected to the input terminal of the tunable laser 3.

[0048] The input of the uplink signal attenuation circuit 1 receives the optical signal output from the cable television network, and after the received optical signal is amplified by the uplink signal amplification circuit 2, it is sent to the tunable laser 3 for processing. The tunable laser 3 then outputs the processed optical signal.

[0049] In this embodiment, after the tunable laser 3 outputs an optical signal, it also needs to transmit the optical power and radio frequency (RF) level values ​​of the optical signal to the optical power and RF level sampling circuit 4. The optical power and RF level sampling circuit 4 adjusts the optical power and RF level values ​​of the output optical signal of the tunable laser 3, and outputs the adjusted optical power and RF level values ​​to the microprocessor circuit 6. The microprocessor circuit 6 controls the attenuation amount of the uplink signal attenuation circuit 1, thereby adjusting the RF input level of the tunable laser 3; on the other hand, it controls the optical power of the optical power control circuit 5, thereby controlling the optical power of the tunable laser 3, and realizing stable control of the optical modulation of the optical node.

[0050] In the uplink signal attenuation circuit 1, the chip used is MADP-007167-0287FT from MACOM Corporation of the United States. It is a low-cost, low-loss, high-isolation, and low-distortion silicon PIN diode that can precisely control the amplitude of the uplink signal through a microprocessor circuit.

[0051] In the uplink signal amplifier circuit 2, the AE427 from RHIC Corporation of South Korea is used. It is a gallium arsenide enhancement mode amplifier chip with small size, high gain, low current consumption, high linearity, low noise, and low cost.

[0052] like Figure 2-5 As shown, the tunable laser 3 uses a coaxial TOSA laser from Xiamen Beilai Co., Ltd., model ZBLLD-PSA-D6120H-55B-2GR(TEC)-5456. The TOSA laser internally uses a high linearity laser chip from AOI, USA, a 1A electronic cooler, and a high-precision thermistor. In this embodiment, a high-efficiency custom heat sink 31 is configured on the outside of the TOSA laser. Through relevant control circuits and control software, the stable output of optical signals of 16 different wavelengths within the 1610±3nm range of the TOSA laser is achieved.

[0053] The heat sink 31 has a convex structure with two mounting holes at both ends and one mounting hole at the top for connecting the heat sink to other devices. One side of the heat sink 31 has a circular opening adapted to the TOSA laser, and the other side has two square openings adapted to the TOSA laser pins. The heat sink 31 is hollow inside, allowing the TOSA laser pins to pass through the circular opening and exit through their respective square openings. A portion of the TOSA laser is housed within the hollow cavity of the heat sink 31. In this embodiment, to improve heat dissipation, the inner surface of the heat sink 31 and the pin surfaces of the TOSA laser should be in close contact, and thermally conductive adhesive should be used between them to ensure the laser chip inside the TOSA laser can operate stably for extended periods.

[0054] The chip used in microprocessor circuit 6 is STC8H3K32S2, which has a built-in 12-bit ADC and 16-bit PWM. The PWM circuit and the external filter circuit can form a 16-bit DAC circuit.

[0055] The optical power and RF level sampling circuit 4 includes an optical signal output power module and an optical signal RF level module.

[0056] The optical signal output power is split by a beam splitter, and the received 5% optical signal is fed into the optical power sampling circuit. The optical power sampling circuit uses a high-sensitivity PIN diode from Xiamen Beilai Co., Ltd. for photoelectric conversion. The PIN diode model is ZBLPD-PN1-70BR. For example, when the output optical power of the optical signal is 2mW, the optical power of the 5% sampled signal is 0.1mW, which is -10dBmW.

[0057] The optical signal RF level module uses the ANALOG DEVICES AD8362 as the root mean square response power detector, which has a measurement range of 65dB and can receive RF signal levels as low as -54dBm.

[0058] Definition of Optical Modulation System (OMI): OMI = Ip / (I b -I th ), where I p I represents the peak modulation current of the laser. b I represents the bias current of the laser; th This represents the laser's threshold current. Since the optical modulation index (OMI) can ignore the laser's threshold current and only consider the laser's bias current, the OMI can be defined as OMI = I. p / I b Adjust the optical power input (e.g., -1dBmW), measure the photoelectric conversion voltage U of the optical receiving PIN tube, and then divide it by the conversion resistance R. z (10kΩ), then the laser bias current value I can be obtained. b =U / R z .

[0059] The radio frequency level value P measured by the radio frequency level sampling circuit o This is a voltage level value in dBm, which can be converted to a voltage level in W using the following formula. o The power value is first converted to a dBW value = P o -30 (dBW), which is equivalent to 10 lgW o =P o -30, and then use the above exponential function to obtain the power value W. o , represented as:

[0060]

[0061] Because the internal resistance R of the light receiver s The load resistance is 50Ω. L The resistance is 50Ω, and the two are connected in parallel. Therefore, the load current I is... L , represented as:

[0062]

[0063]

[0064] Therefore, the total current I is obtained. all , represented as:

[0065]

[0066] Given that the signal is a sine wave, its peak modulation current I p , represented as:

[0067]

[0068] The operating current value I of the tunable laser b =U / R z R z =10kΩ, expressed as:

[0069] I b =U / (10×10³)(A) =U / 10(mA)

[0070] OMI (Optical Modem) is represented as:

[0071]

[0072] As long as the photoelectric conversion voltage value U (V) and the radio frequency level value P are measured... o The modulation index (OMI) of the optical node can be calculated from (dBm).

[0073] When stabilizing the optical output power, adjusting the laser's bias current will cause a change in the optical modulation index (OMI). By adjusting the attenuation of the uplink signal attenuation circuit based on the RF level sampling circuit, and by adjusting the RF input level of the tunable laser through a microprocessor circuit, stable control of the optical modulation index can be achieved.

[0074] The stable control of optical modulation is achieved by controlling the output optical power and RF level of the tunable laser to keep the optical modulation in a relatively stable state.

[0075] In this embodiment of the solution, the control range of the output optical power of the tunable laser is required to be ±0.05mW of the nominal value, and the range of optical modulation index (OMI) is ±0.5% of the nominal value.

[0076] The relationship between the photoelectric conversion voltage value of the sampling voltage for the output optical power of a tunable laser and the output optical power of the tunable laser is shown in Table 1 below:

[0077] Table 1

[0078]

[0079] From Table 1, the formula for calculating the output optical power of a tunable laser can be constructed, as follows:

[0080] P out =3.5397*U-0.0001(1)

[0081] Among them, P out The output optical power of the tunable laser is expressed in mW; U represents the photoelectric conversion voltage of the optical power, expressed in V.

[0082] In this embodiment, the A / D sampling circuit for optical power uses a 12-bit ADC with a reference voltage of 5V and a voltage sampling accuracy of 1.22mV. The calculation accuracy of the output optical power of the tunable laser is approximately 0.0043mW.

[0083] The relationship between the output RF level and sampling voltage of the tunable laser is shown in Table 2 below:

[0084] Table 2

[0085]

[0086]

[0087] From Table 2, a formula for calculating the output RF level of a tunable laser can be constructed, expressed as:

[0088] P = V out / 0.05-60(2)

[0089] Where P represents the output radio frequency level of the tunable laser, in dBm; V out This indicates the sampled voltage value, in units of V.

[0090] In this embodiment, the A / D sampling circuit for the radio frequency level is a 12-bit ADC with a voltage sampling accuracy of 1.22mV and a radio frequency level calculation accuracy of approximately 0.0244dBm.

[0091] In this embodiment, a tunable laser with an output optical power of 2mW is used. The optical power control circuit adopts a 16-bit DAC circuit, with a reference voltage of 5V and a control voltage accuracy of approximately 0.076mV. The relationship between the change in the output optical power of the tunable laser and the change in the output voltage of the optical power control circuit is 1.5mV / 0.05mW, which is equivalent to 0.3mW / 0.01mW. From the accuracy of the control voltage, it can be seen that the control accuracy of the output optical power of the tunable laser is less than 0.01mW, which can realize the control of the output optical power of the tunable laser, so that the output optical power of the tunable laser can be controlled within ±0.05mW of the nominal value.

[0092] In software implementation, RF level control is achieved by controlling the DAC circuit in the microprocessor circuit to control the attenuation value of the RF level control circuit, thereby enabling different RF levels to be input to the tunable laser. The DAC circuit of the optical power control circuit uses a 16-bit DAC with a reference voltage of 5V. The control voltage accuracy of the DAC circuit of the optical power control circuit is approximately 0.076mV. The relationship between the control voltage and the attenuation value of the RF level is approximately 20mV / 0.05dB. From the control voltage accuracy, it can be seen that the control accuracy of the RF level attenuation value can reach within 0.01dB.

[0093] In summary, the formula for calculating the light modulation degree in this embodiment is expressed as follows:

[0094]

[0095] Where OMI represents optical modulation; U represents the photoelectric conversion voltage value of optical power; and P represents the output radio frequency level value of the tunable laser.

[0096] In this embodiment, the nominal optical modulation degree is 51.15%. When the optical power is taken as nominal value +0.05mW, nominal value and nominal value -0.05mW, the OMI values ​​obtained when the RF level is taken as negative bias 0.05dB, standard and positive bias 0.05dB under these three optical power values ​​are shown in Table 3 below:

[0097] Table 3

[0098]

[0099] As shown in Table 3 above, when the RF level is positively or negatively biased by 0.05dB, the maximum deviation of the OMI value is 0.315, which meets the requirement of ±0.5 of the nominal value.

[0100] With the same optical power value, the OMI values ​​obtained when the RF level is negatively biased by 0.03dB, standard, and positively biased by 0.03dB are shown in Table 4 below:

[0101] Table 4

[0102]

[0103]

[0104] As shown in Table 4 above, when the RF level is positively or negatively biased by 0.03 dBm, the maximum deviation of the OMI value is 0.197, and the deviation is within 0.2.

[0105] In summary, when the output optical power of the tunable laser is controlled within ±0.05mW of the nominal value, the optical modulation degree can be controlled within ±0.5% of the nominal value by adjusting the RF level. To avoid too frequent adjustments, in this embodiment, no adjustment is made when the laser output optical power is within ±0.05mW of the nominal value, and adjustment is made when it exceeds this range. During adjustment, the output optical power is controlled within ±0.02mW of the nominal value, and the RF level is not adjusted when the optical modulation degree is within ±0.5% of the nominal value. The RF level is adjusted when it exceeds this range, and the optical modulation degree is controlled within ±0.3% of the nominal value after adjustment.

[0106] The beneficial effects of this embodiment are:

[0107] 1. The RFoG optical node with a tunable DWDM wavelength RFoG optical node optical modulation stabilization system provides an effective solution to the OBI (optical beat frequency interference) noise problem in the backhaul channel of a bidirectional HFC network.

[0108] 2. This invention significantly reduces the procurement cost of transmission equipment for cable TV operators by adding a customized heat sink to a coaxial TOSA laser with a built-in semiconductor cooler and thermistor, compared to the original butterfly-packaged wavelength-tuned DFB laser.

[0109] 3. This invention controls the optical output power and optical modulation of a stable optical node through relevant control circuits and software. A tunable DWDM wavelength optical node with stable optical modulation can improve the transmission quality of cable television networks and reduce the operation and maintenance costs of cable television operators.

[0110] Example 2

[0111] The optical modulation stabilization system for a tunable DWDM wavelength RFoG optical node provided in this embodiment differs from that in Embodiment 1 in that:

[0112] This embodiment adjusts the optical power and radio frequency level of the tunable laser to achieve stable optical modulation, such as... Figure 6 As shown, it specifically includes:

[0113] A1. Sample the optical power value of the output optical signal of the tunable laser and calculate the first actual optical power of the tunable laser according to formula (1);

[0114] A2. Calculate the first deviation nominal value between the first actual optical power value and the preset optical power value, and determine whether the first deviation nominal value is within ±0.05mW. If yes, proceed to step A6; otherwise, calculate the first optical power control value through the first optical power deviation value.

[0115] The conversion method is as follows: The conversion formula for DAC control values ​​in optical power control is: D 光 =D 0光 -(2-P out ) / 0.0025, where P out D is the output optical power of the laser. 0光 The control value is the same as the previous one. At startup, D... 0光 This is based on the actual preset value.

[0116] It should be noted that the preset optical power value can be set according to the actual situation or it can be the optical power value of the industry standard; and the deviation from the nominal value is calculated as the absolute value of the first actual optical power value minus the preset optical power value, and the deviation from the nominal value can also be the difference.

[0117] A3. The first optical power control value is sent to the optical power control circuit via the microprocessor circuit;

[0118] A4. Sample the optical power value of the output optical signal of the tunable laser and calculate the second actual optical power of the tunable laser according to formula (1);

[0119] A5. Calculate the second deviation from the preset optical power value, and determine whether the second deviation is within ±0.02mW. If not, calculate the second optical power control value and continue to execute step A3.

[0120] A6. If the first deviation from the nominal value is within ±0.05mW, the radio frequency level of the output optical signal of the tunable laser is sampled, the first actual level value of the tunable laser is calculated according to formula (2), and the first optical modulation index (OMI) value of the tunable laser is calculated according to formula (3).

[0121] A7. Calculate whether the first OMI deviation value between the first optical modulation OMI value and the preset OMI value is within ±0.5%. If yes, then end; if no, then calculate the first radio frequency level control value.

[0122] The calculation method for the first RF level control DAC control value D is as follows:

[0123] P 目标 =30+20*log(51.15*U / 400000), where U is the sampling voltage of the laser output optical power.

[0124] D 电 =D 0电 +(PP 目标 ) / 0.00019, where P is the current value of the radio frequency level, and D 0电 The control value is the same as the previous one. At startup, D... 0电 This is a preset value.

[0125] It should be noted that the preset OMI value can be set according to the actual situation or it can be the industry standard OMI value; and the calculated OMI deviation value is the absolute value of the first brightness adjustment OMI value minus the preset OMI value. The OMI deviation value can also be a difference.

[0126] A8. The microprocessor circuit sends the first radio frequency level control value to the uplink signal attenuation circuit;

[0127] A9. Sample the radio frequency level of the output optical signal of the tunable laser, calculate the second actual level of the tunable laser according to formula (2), and calculate the second optical modulation index (OMI) value of the tunable laser according to formula (3).

[0128] A10. Calculate whether the second OMI deviation value between the second optical modulation OMI value and the preset OMI value is within ±0.3%. If not, calculate the second RF level control value and continue to execute step A8; if yes, end.

[0129] This embodiment uses relevant control circuits and software to control the optical output power and optical modulation of a stable optical node. A tunable DWDM wavelength optical node with stable optical modulation can improve the transmission quality of cable TV networks, reduce the operation and maintenance costs of cable TV operators, and has strong market competitiveness and a good market prospect.

[0130] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A tunable DWDM wavelength RFoG optical node optical modulation stabilization system, wherein the optical modulation stabilization system is installed at the user end, characterized in that, It includes an uplink signal attenuation circuit, an uplink signal amplification circuit, a tunable laser, an optical power and RF level sampling circuit, an optical power control circuit, and a microprocessor circuit; The output of the uplink signal attenuation circuit is connected to the input of the uplink signal amplification circuit. The output of the uplink signal amplification circuit is connected to the input of the tunable laser. The output of the tunable laser is connected to the input of the optical power and RF level sampling circuit. The output of the optical power and RF level sampling circuit is connected to the input of the microprocessor circuit. The output of the microprocessor circuit is connected to the input of the optical power control circuit and the input of the uplink signal attenuation circuit, respectively. The output of the optical power control circuit is connected to the input of the tunable laser. The input of the uplink signal attenuation circuit receives the optical signal output from the cable television network, and after the received optical signal is amplified by the uplink signal amplification circuit, it is sent to the tunable laser for processing. The tunable laser then outputs the processed optical signal. The optical power and RF level sampling circuit acquires the optical power and RF level values ​​of the output optical signal of the tunable laser, adjusts the optical power and RF level values, and outputs the adjusted optical power and RF level values ​​to the microprocessor circuit. The microprocessor circuit controls the attenuation of the uplink signal attenuation circuit, thereby adjusting the RF input level of the tunable laser; on the other hand, it controls the optical power of the optical power control circuit, thereby controlling the optical power of the tunable laser, and realizing stable control of the optical modulation of the optical node. The specific steps for adjusting the optical power of the tunable laser output optical signal are as follows: A1. Calculate the first actual optical power of the output optical signal of the tunable laser; A2. Calculate the first deviation from the preset optical power value of the first actual optical power value and determine whether the first deviation from the preset optical power value is within ±0.05mW. If not, calculate the first optical power control value. A3. The first optical power control value is sent to the optical power control circuit via the microprocessor circuit; A4. Calculate the second actual optical power of the output optical signal of the tunable laser; A5. Calculate the second deviation from the preset optical power value, and determine whether the second deviation is within ±0.02mW. If not, calculate the second optical power control value and continue to execute step A3. The adjustment of the radio frequency level of the tunable laser specifically involves: A6. If the first deviation from the nominal value is within ±0.05mW, calculate the first actual level value of the optical signal at the location of the tunable laser, and calculate the first optical modulation index (OMI) value of the tunable laser based on the first actual level value. A7. Calculate whether the first OMI deviation value between the first optical modulation OMI value and the preset OMI value is within ±0.5%. If yes, end; if no, calculate the first RF level control value. A8. The microprocessor circuit sends the first radio frequency level control value to the uplink signal attenuation circuit; A9. Calculate the second actual level value of the output optical signal of the tunable laser, and calculate the second optical modulation index (OMI) value of the tunable laser based on the second actual level value; A10. Calculate whether the second OMI deviation value between the second optical modulation OMI value and the preset OMI value is within ±0.3%. If not, calculate the second RF level control value and continue to execute step A8; if yes, end. In step A5, it is determined whether the second deviation from the nominal value is within ±0.02mW. If so, step A6 is executed.

2. The optical modulation stabilization system for a tunable DWDM wavelength RFoG optical node according to claim 1, characterized in that, The tunable laser is a TOSA laser, which is equipped with a heat sink to achieve stable output of optical signals of 16 different wavelengths within the range of 1610±3nm.

3. The optical modulation stabilization system for a tunable DWDM wavelength RFoG optical node according to claim 2, characterized in that, The chip model of the uplink signal attenuation circuit is MADP-007167-0287FT; the chip model of the uplink signal amplification circuit is AE427; and the chip model of the microprocessor circuit is STC8H3K32S2.

4. The optical modulation stabilization system for a tunable DWDM wavelength RFoG optical node according to claim 1, characterized in that, The optical power of the output optical signal of the tunable laser is expressed as: P out =3.5397*U -0.0001 Among them, P out The output optical power of the tunable laser is represented by ; U represents the photoelectric conversion voltage value of the optical power.

5. The optical modulation stabilization system for a tunable DWDM wavelength RFoG optical node according to claim 1, characterized in that, The radio frequency level value of the output optical signal of the tunable laser is expressed as: P=V out / 0.05-60 Where P represents the output radio frequency level of the tunable laser; V out This indicates the sampled voltage value.

6. The optical modulation stabilization system for a tunable DWDM wavelength RFoG optical node according to claim 1, characterized in that, The optical modulation scheme of the optical node is expressed as follows: WATER= (%) Where OMI represents optical modulation; U represents the photoelectric conversion voltage value of optical power; and P represents the output radio frequency level value of the tunable laser.

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