An optical digital-to-analog conversion system based on directly modulated laser and optical coupler array

Abstract

The present invention discloses an optical digital-to-analog conversion system based on a direct-modulated laser and an optical coupler array, which includes a digital signal array, a direct-modulated laser array, an optical fiber delay array, an optical coupler array, an optoelectronic filter and a control system, wherein the digital signal array generates a binary electrical digital quantity to be converted, which is converted into an optical signal by the direct-modulated laser array, enters the optical fiber delay array for time alignment, and then is converted into an analog optical power signal after coupling and beam splitting by the optical coupler array, and finally the optical beat frequency signal is filtered out by the optoelectronic filter to output an analog optical signal, and the control system controls the output power of each laser in the direct-modulated laser array to be equal and stable, so that the output analog signal meets the conversion requirements. The analog-to-digital conversion method used by the optical digital-to-analog conversion system of the present invention is implemented in the optical domain through a 2×2 optical coupler array, and is not limited by the bandwidth of electronic devices.

Description

Technical Field

[0001] The invention relates to the technical field of optical digital-to-analog conversion, and in particular to an optical digital-to-analog conversion system based on a direct-modulated laser and an optical coupler array. Background Art

[0002] The Yuen 2000 encryption protocol is a physical layer encryption technology that improves the security of optical fiber communication. It mainly uses the digital-to-analog conversion (DAC) method to map binary signals into multi-level signals, and then uses the noise sensitivity of multi-level signals to submerge the signals in the inherent noise of the laser, thereby realizing the channel difference between legitimate users and eavesdropping users and obtaining the secure transmission conditions of the physical layer information of the optical network. In the literature [K.Ohhata, O.Hirota, M.Honda, et al. 10-Gb / s Optical Transceiver Using the Yuen 2000 Encryption Protocol [J]. Journal of Lightwave Technology, 2010, 28 (18): 2714-2723.], a special DAC electronic chip was designed by using the dedicated technology of 0.25μm SiGe BiCMOS, and a 10Gb / s, 300km optical fiber secure transmission experiment was realized. The DAC is a device that converts electrical digital signals into analog signals. The relationship between its input and output is:

[0003]

[0004] In formula (1), A is the output analog quantity, E is the reference quantity, and a n ∈{0,1} is the input binary digital value, and N is the number of DAC bits. However, the design of electronic DAC chips is complex and is limited by electronic bottlenecks, which affects the improvement of Yuen 2000 encryption performance. Summary of the invention

[0005] Based on the defects of the above-mentioned prior art, the present invention proposes an optical digital-to-analog conversion system based on a directly modulated laser and an optical coupler array, which aims at the demand for high-speed and high-bit resolution digital-to-analog conversion of high-order modulation in the Yuen 2000 encryption protocol, introduces an optical digital-to-analog conversion system to realize the function of an electronic DAC chip, without the need for special high-speed circuit design. It is not only simple to implement, but also can overcome the electronic bottleneck of traditional electronic DAC chips.

[0006] According to the technical solution of the present invention, an optical digital-to-analog conversion system based on a direct-modulated laser and an optical coupler array is provided, which includes a digital signal array, a direct-modulated laser array, an optical fiber delay array, an optical coupler array, an optoelectronic filter and a control system; wherein the digital signal array generates a binary electrical digital quantity to be converted, which is converted into an optical signal by the direct-modulated laser array, enters the optical fiber delay array for time alignment, and then is converted into an analog optical power signal after coupling and splitting by the optical coupler array, and finally the optical beat frequency signal is filtered out by the optoelectronic filter to output an analog optical signal.

[0007] Among them, the digital signal array is connected to the direct-modulation laser array, which is used to generate the binary electrical digital quantity to be converted; the direct-modulation laser array is connected to the fiber delay array, which is used to convert the binary electrical digital quantity into an optical signal, and the fiber delay array is connected to the optical coupler array, which is used to perform time alignment of the optical signal; the optical coupler array is connected to the photoelectric filter, which is used to convert the optical signal into an analog optical power signal after coupling and splitting; the photoelectric filter is used to eliminate the optical beat frequency signal and output the analog optical signal.

[0008] The control system controls the output power of each laser in the direct-modulation laser array to be equal and stable, so that the output analog signal meets the conversion requirements; the control system detection optical fiber is connected to the optical coupler array to detect the optical power output by the direct-modulation laser, and is connected to the direct-modulation laser via a laser control cable to control the output power of the direct-modulation laser, so as to achieve equal and stable output power of each laser in the direct-modulation laser array.

[0009] Furthermore, the digital signal array comprises N binary electrical digital quantities to be converted from digital to analog, and is output to the direct modulated laser array for photoelectric conversion.

[0010] The direct-modulated laser array includes N direct-modulated lasers with an output power range of 1mW to 40mW, an output wavelength range of 1525nm to 1565nm, and a signal adjustment rate of 1Gbps to 40Gbps, and is used to convert N input digital electrical signals into N parallel optical signals of different wavelengths and output them to the optical fiber delay array.

[0011] In the above optical digital-to-analog conversion system, the fiber delay array includes N fiber delays, which delay the input N optical signals of different wavelengths respectively, and output them to the optical coupler array to ensure the alignment of the optical signals. Furthermore, the optical coupler array includes N 2×2 optical couplers with a splitting ratio of 1:1, which couple the input N optical signals of different wavelengths in sequence and divide them into two signal outputs with equal power. The first optical signal is output from output port 1 to the detection port of the control system; the second optical signal is output from output port 2 to the input port 1 of the next 2×2 optical coupler.

[0012] In addition, the optoelectronic filter in the optical digital-to-analog conversion system is used to filter the optical signal input by the optical coupler array to obtain the converted optical power analog signal. The control system monitors the optical signals input by the N detection ports and controls the output power of the direct-modulated laser array through the N control ports, so that the output power of the N direct-modulated lasers in the direct-modulated laser array is equal and stable.

[0013] Compared with the prior art, the optical digital-to-analog conversion system based on the direct-modulated laser and the optical coupler array of the present invention has the following advantages:

[0014] 1. The analog-to-digital conversion method used by the optical digital-to-analog conversion system of the present invention is implemented in the optical domain through a 2×2 optical coupler array, is not limited by the bandwidth of electronic devices, and is easily compatible with existing high-speed optical communication systems.

[0015] 2. The optical digital-to-analog conversion structure of the present invention has the advantages of simple structure, low power consumption, certain scalability, and easy realization of large-scale optoelectronic integration in the preparation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 1 is a structural block diagram of an optical digital-to-analog conversion system according to the present invention; in the figure, solid connecting lines represent optical fiber connections, and dashed connecting lines represent electrical signal connections.

[0017] Figure 2 It is a schematic diagram of an analog signal processed and output by the optical digital-to-analog conversion system of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the scope of protection of the present invention should not be limited to the following specific structures or components or specific parameters.

[0019] The optical digital-to-analog conversion system based on a direct-modulated laser and an optical coupler array provided by the present invention comprises a digital signal array, a direct-modulated laser array, an optical fiber delay array, an optical coupler array, an optoelectronic filter and a control system, wherein the digital signal array generates a binary electrical digital quantity to be converted, which is converted into an optical signal by the direct-modulated laser array, enters the optical fiber delay array for time alignment, and then is converted into an analog optical power signal after coupling and beam splitting by the optical coupler array, and finally the optical beat frequency signal is filtered out by the optoelectronic filter to output an analog optical signal, and the control system controls the output power of each laser in the direct-modulated laser array to be equal and stable, so that the output analog signal meets the conversion requirements. The analog-to-digital conversion method used by the optical digital-to-analog conversion system of the present invention is implemented in the optical domain through a 2×2 optical coupler array, and is not limited by the bandwidth of electronic devices.

[0020] Furthermore, the digital signal array is connected to the direct-modulation laser array to generate the binary electrical digital quantity to be converted; the direct-modulation laser array is connected to the fiber delay array to convert the binary electrical digital quantity into an optical signal, and the fiber delay array is connected to the optical coupler array to perform time alignment of the optical signal; the optical coupler array is connected to the photoelectric filter to convert the optical signal into an analog optical power signal after coupling and splitting; the photoelectric filter is used to eliminate the light-removing beat frequency signal and output the analog optical signal. The control system detection optical fiber is connected to the optical coupler array to detect the optical power output by the direct-modulation laser, and is connected to the direct-modulation laser via the laser control cable to control the output power of the direct-modulation laser, so as to achieve equal and stable output power of each laser in the direct-modulation laser array.

[0021] Furthermore, the digital signal array comprises N binary electrical digital quantities to be converted from digital to analog, and is output to the direct modulated laser array for photoelectric conversion.

[0022] The direct-modulated laser array includes N direct-modulated lasers with an output power range of 1mW to 40mW, an output wavelength range of 1525nm to 1565nm, and a signal adjustment rate of 1Gbps to 40Gbps, and is used to convert N input digital electrical signals into N parallel optical signals of different wavelengths and output them to the optical fiber delay array.

[0023] In the above optical digital-to-analog conversion system, the fiber delay array includes N fiber delays, which delay the input N optical signals of different wavelengths respectively, and output them to the optical coupler array to ensure the alignment of the optical signals. Furthermore, the optical coupler array includes N 2×2 optical couplers with a splitting ratio of 1:1, which couple the input N optical signals of different wavelengths in sequence and divide them into two signal outputs with equal power. The first optical signal is output from output port 1 to the detection port of the control system; the second optical signal is output from output port 2 to the input port 1 of the next 2×2 optical coupler.

[0024] In addition, the optoelectronic filter in the optical digital-to-analog conversion system is used to filter the optical signal input by the optical coupler array to obtain the converted optical power analog signal. The control system monitors the optical signals input by the N detection ports and controls the output power of the direct-modulated laser array through the N control ports, so that the output power of the N direct-modulated lasers in the direct-modulated laser array is equal and stable.

[0025] The optical digital-to-analog conversion system based on a directly modulated laser and an optical coupler array of the present invention is further described below in conjunction with the accompanying drawings.

[0026] like Figure 1 As shown, the optical digital-to-analog conversion system based on the direct-modulated laser and the optical coupler array includes a digital signal input array, a direct-modulated laser array, an optical fiber delay array, an optical coupler array, an optoelectronic filter and a control system. The digital signal array includes N digital signals a1, a2, ..., a N , specifically including N binary electrical digital quantities to be converted into digital-to-analog quantities, converting digital signals a1, a2, ..., a N The output is sent to the direct-modulation laser array for photoelectric conversion. The direct-modulation laser array includes N direct-modulation lasers, namely direct-modulation laser 1, direct-modulation laser 2, ..., direct-modulation laser N. The output power range of each direct-modulation laser is 1mW to 40mW, the output wavelength range is 1525nm to 1565nm, and the signal adjustment rate is 1Gbps to 40Gbps. It is used to convert the N input digital electrical signals into N parallel optical signals of different wavelengths, and output them to the optical fiber delay array. The optical fiber delay array includes N optical fiber delays, namely optical fiber delay 1, optical fiber delay 2, ..., optical fiber delay N. Each optical fiber delay respectively delays the input N optical signals of different wavelengths, and outputs them to the optical coupler array to ensure signal alignment. Figure 1As shown, optical fiber delay device 1 outputs the optical delay signal to the input end 2 of optical 2×2 coupler 1, optical fiber delay device 2 outputs the optical delay signal to the input end 2 of optical 2×2 coupler 2, optical fiber delay device 3 outputs the optical delay signal to the input end 2 of optical 2×2 coupler 3, ..., optical fiber delay device N outputs the optical delay signal to the input end 2 of optical 2×2 coupler N.

[0027] The optical coupler array includes N optical couplers, that is, N 2×2 optical couplers with a splitting ratio of 1:1, as shown in the figure 2×2 optical coupler 1, 2×2 optical coupler 2, ..., 2×2 optical coupler N; each optical coupler couples the input N optical signals of different wavelengths in sequence, and outputs them into two signals with equal power. The first optical signal is output from output port 1 to the corresponding detection port of the control system; the second optical signal is output from output port 2 to input port 1 of the next 2×2 optical coupler, and so on, and finally the optical signal is output to the optoelectronic filter. For example, the output port 1 of the 2×2 optical coupler 1 is output to the detection port 1 of the control system, and the output port 2 of the 2×2 optical coupler 1 is output to the input port 1 of the 2×2 optical coupler 2; the output port 1 of the 2×2 optical coupler 2 is output to the detection port 2 of the control system, and the output port 2 of the 2×2 optical coupler 2 is output to the input port 1 of the 2×2 optical coupler 3, .... The optical signal power can be expressed as:

[0028]

[0029] In the formula (2), [·]* represents a conjugation operation, a n ∈{0,1} represents a binary digital quantity, A n (λ n ) indicates the wavelength is λ n The output light amplitude of the directly modulated laser, P n (λ n )=A n (λ n )[A n (λ n )] * Indicates wavelength as λ n The output optical power of the directly modulated laser is represents the DC component of the optical signal, Indicates different laser wavelengths λ m , n (m≠n) the beat frequency signal, C mn Represents the beat frequency coefficient.

[0030] The photoelectric filter filters the optical signal input by the optical coupler array to obtain the converted optical power analog signal:

[0031]

[0032] Preferably, the control system monitors the optical signals input from the N detection ports, and controls the output power of the direct-modulated laser array through the N control ports respectively (control port 1 controls direct-modulated laser 1, control port 2 controls direct-modulated laser 2, ... control port N controls direct-modulated laser N), so that the output power of the N direct-modulated lasers in the direct-modulated laser array is equal to P, that is,

[0033] P1(λ1)=P2(λ2)=LP n (λ n )L=P N (λ N )=P (4)

[0034] Then there is

[0035]

[0036] like Figure 2 The schematic diagram of the analog signal processed and output by the optical digital-to-analog conversion system of the present invention is shown in the figure, where the horizontal axis represents time in ps, the left side of the vertical axis represents the output analog power in mW, and the right side of the vertical axis represents the binary digital component corresponding to the analog quantity; wherein each direct-modulated laser in the laser array has an output power of 10mW, a signal modulation rate of 10Gbps, an input digital sequence N=5, and the maximum output optical power of the photoelectric filter is 48mW. It can be obtained from the figure that the combination of the direct-modulated laser and the optical coupler array can realize 10Gbps, 5-bit optical DAC conversion, and obtain a 32-order multi-level modulation signal.

[0037] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. It can be understood by a person of ordinary skill in the art that various modifications can be made in form and details without departing from the spirit and scope of the present invention defined in the appended claims.

Claims

1. An optical digital-to-analog conversion system based on a directly modulated laser and an optical coupler array, characterized in that: It includes a digital signal array, a direct-modulated laser array, an optical fiber delay array, an optical coupler array, an optoelectronic filter and a control system, wherein the digital signal array generates a binary electrical digital quantity to be converted, which is converted into an optical signal by the direct-modulated laser array, enters the optical fiber delay array for time alignment, and then is converted into an analog optical power signal after coupling and splitting by the optical coupler array, and finally the optical beat frequency signal is filtered out by the optoelectronic filter to output an analog optical signal; The optical coupler array includes N 2×2 optical couplers with a splitting ratio of 1:1, which respectively couple the input N optical signals of different wavelengths in sequence and output them as two signals with equal power. The first optical signal is output from output port 1 to the detection port of the control system. The second optical signal is output from output port 2 to input port 1 of the next 2×2 optical coupler; The control system monitors the optical signals inputted from the N detection ports, and controls the output power of the direct-modulation laser array respectively through the N control ports, so that the output powers of the N direct-modulation lasers in the direct-modulation laser array are equal and stable.

2. The optical digital-to-analog conversion system according to claim 1, characterized in that: The digital signal array is connected to the direct-modulation laser array, which is used to generate the binary electrical digital quantity to be converted. The direct-modulation laser array is connected to the optical fiber delay array, which is used to convert the binary electrical digital quantity into an optical signal. The optical fiber delay array is connected to the optical coupler array, which is used to perform time alignment of the optical signal. The optical coupler array is connected to the photoelectric filter, which is used to convert the optical signal into an analog optical power signal after coupling and splitting. The photoelectric filter is used to eliminate the optical beat frequency signal and output the analog optical signal.

3. The optical digital-to-analog conversion system according to claim 1 or 2, characterized in that: The control system controls the output power of each laser in the direct-modulated laser array to be equal and stable, so that the output analog signal meets the conversion requirements.

4. The optical digital-to-analog conversion system according to claim 3, characterized in that: The detection optical fiber in the control system is connected to the optical coupler array for detecting the optical power output by the direct-modulated laser. At the same time, it is connected to the direct-modulated laser via a laser control cable for controlling the output power of the direct-modulated laser to achieve equal and stable output power of each laser in the direct-modulated laser array.

5. The optical digital-to-analog conversion system according to claim 1, characterized in that: The digital signal array includes N binary electrical digital quantities to be converted from digital to analog, and is output to the direct-modulated laser array for photoelectric conversion.

6. The optical digital-to-analog conversion system according to claim 1, characterized in that: The direct-modulation laser array includes N direct-modulation lasers with an output power range of 1 mW to 40 mW, an output wavelength range of 1525 nm to 1565 nm, and a signal adjustment rate of 1 Gbps to 40 Gbps. It is used to convert N input digital electrical signals into N parallel optical signals of different wavelengths and output them to the optical fiber delay array.

7. The optical digital-to-analog conversion system according to claim 1, characterized in that: The optical fiber delay array includes N optical fiber delays, which respectively delay N input optical signals of different wavelengths and output them to the optical coupler array to ensure the alignment of the optical signals.

8. The optical digital-to-analog conversion system according to claim 1, characterized in that: The photoelectric filter filters the optical signal input by the optical coupler array to obtain a converted optical power analog signal.

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