CN111147145A

CN111147145A - Large-key space chaotic optical communication transceiver

Info

Publication number: CN111147145A
Application number: CN201911244716.5A
Authority: CN
Inventors: 郭园园; 吴梅; 王龙生; 王安帮; 王云才
Original assignee: Taiyuan University of Technology
Current assignee: Taiyuan University of Technology
Priority date: 2019-12-06
Filing date: 2019-12-06
Publication date: 2020-05-12
Anticipated expiration: 2039-12-06
Also published as: CN111147145B

Abstract

The invention discloses a large-key space chaotic optical communication transceiver, belonging to the technical field of secret optical communication; the key space is increased by increasing the number of the external cavities, the structure is complex, the key space is easy to be interfered by the environment, the key space increased by pseudo-random code modulation cannot play the hardware encryption advantage special for chaotic secret communication, the complexity of a feedback loop is increased, the cost of the key space is high, and the integration and the scale production are not convenient; the invention provides a large-key-space chaotic optical communication transceiver, wherein a key space is formed by combining feedback intensity of a DFB semiconductor laser and key parameters of a driving current and a random filtering module, the random filtering module replaces a traditional feedback mirror to realize a random selection function after a light path range encodes a spectrum, the key space of the chaotic optical communication transceiver is greatly improved, the secret communication of a legal user is met, the stealing difficulty of an illegal user is increased, the time delay characteristic is effectively hidden, the consistency of hardware is ensured, the chaotic synchronization is easy, and the large-scale production is convenient.

Description

Large-key space chaotic optical communication transceiver

Technical Field

The invention relates to the technical field of secret optical communication, in particular to a large-key space chaotic optical communication transceiver.

Background

The chaotic optical communication has the advantages of hardware encryption, compatibility with the existing optical communication system, suitability for high-speed (Gbit/s) and long-distance (km) secret communication and the like, and is receiving wide attention. The key of chaotic optical secret communication is chaotic synchronization between a chaotic laser receiver and a transmitter, which requires that the structural parameters of the receiver and the transmitter are completely matched or within a certain parameter mismatch range (Phys. Rev. E, Vol. 69, P.056226, 2004). For both parties of legal communication, the hardware structure parameters of the transceiver are generally used as keys. The larger the key space composed of key parameters is, the longer the time required for an eavesdropper to crack information is, the lower the probability of obtaining correct information is, the slower the cracking speed is, and finally, the information is difficult to crack. Thus, one of the key issues with chaotic secure communications is increasing the key space of the transceiver.

The chaotic optical communication transceivers commonly used are classified into three types: the first is a chaotic optical communication transceiver based on an optical fiber laser, and the rate of the type of the transceiver is low (IEEE Photonic Tech L, Vol.12, P.269-271, 2000.), which is not suitable for high-speed secret communication; secondly, although the rate of the chaotic optical communication transceiver based on the photoelectric feedback oscillator can reach Gbit/s (Nature, Vol.438 (7066), P.343-346, 2005), the chaotic optical communication transceiver has a complex structure, needs high-bandwidth filters and other devices, and is high in cost and not beneficial to practicability; and the third is a chaotic optical communication transceiver based on a semiconductor laser, which is the most commonly used transceiver in chaotic secure communication research at present (Phys.Rev. A, Vol. 94, P.061803, 2016) due to simple structure and low cost. However, for an external cavity feedback semiconductor laser as a transceiver, an eavesdropper can deduce the bias current loaded by the laser by analyzing the relaxation oscillation frequency of the laser by measuring the power spectrum of the chaotic light carrier on a communication line; the intercepted chaotic carrier is subjected to autocorrelation operation, and external cavity length information can be obtained from an autocorrelation curve; after the two parameters are stolen, the feedback strength can be broken through 'exhaustive attack', namely the feedback strength is continuously adjusted by using the variable optical attenuator, and chaos synchronization of an eavesdropper and a transmitter can be finally realized. Therefore, only three structural parameters of bias current, external cavity length and feedback strength are used as keys, the key space is too small, and an eavesdropper can easily crack and acquire correct information. If the transceiver has more key parameters, namely the key space is large enough, secret communication among a large number of legal users can be met, and the stealing difficulty of illegal users can be increased.

Currently, the research schemes for increasing the key space mainly include the following three categories: the first is to increase the key space by increasing the number of external cavities, and to use a semiconductor laser with multiple external cavity feedback or chirped fiber grating distributed feedback functions as a chaotic optical communication transceiver (Phys. Rev. E, Vol. 78, P.016210.1-6, 2008; Opt. Express, Vol.27, P.3065-3073, 2019). However, the increase of the number of the external cavities makes the space structure of the chaotic communication transceiver more complex, is easily interfered by the environment, reduces the robustness of communication, and can hide the external cavity length information only if the parameters such as the feedback strength, the external cavity length, the bias current and the like are selected in certain specific ranges, which actually limits the effective parameter key space; the second is to increase the key space by modulating the feedback cavity length with pseudo random code, and to modulate the cavity length or phase information of the external cavity feedback laser by using a pre-set pseudo random code sequence as a private key (Phys. Rev. Lett., Vol. 107, P.1-4,2011; IEEE photon. Technol. Lett., Vol.27, P.326-329, 2015). However, for an external cavity semiconductor laser with a simple structure, the safety of the external cavity semiconductor laser depends on a private key rather than the physical parameters of the device, and the hardware encryption advantage unique to chaotic secret communication cannot be exerted; thirdly, the key space is increased by increasing the complexity of the feedback loop, and a controllable optoelectronic device is embedded in the feedback loop, so that the number of devices for controlling the chaotic state is increased (Opt Express, Vol 24, P.23439-23449, 2016). However, the method for increasing the key space by increasing the complexity of the inserted device has high cost, is inconvenient for integration and large-scale production, and has difficulty in ensuring the consistency of hardware and difficulty in realizing chaotic synchronization of both parties of legal communication.

In summary, in the existing scheme of increasing the key space of the transceiver, the key space is increased by increasing the number of external cavities, the structure is complex, the transceiver is easily interfered by the environment, and the time delay information can be hidden in the effective interval; the pseudo-random code modulation is used for enhancing the key space, the security of the key space depends on a private key rather than the physical parameters of a device, and the special hardware encryption advantage of chaotic secret communication cannot be exerted; the key space is increased by increasing the complexity of the feedback loop, the cost is high, the integration and the scale production are not convenient, the hardware consistency is difficult to ensure, and the chaos synchronization of both sides of the legal communication is difficult to realize.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a large-key space chaotic optical communication transceiver which is mainly used for greatly improving the key space of the chaotic optical communication transceiver, meeting the requirement of secret communication among a large number of legal users and increasing the stealing difficulty of illegal users.

In order to achieve the purpose, the invention provides the following technical scheme:

a large-key space chaotic optical communication transceiver comprises a DFB semiconductor laser, a beam splitter, a coupler and a random filtering module, wherein the random filtering module is used as a feedback mirror to realize the random selection function of a light path range after spectrum coding; the key space of the chaotic optical communication transceiver is formed by the feedback intensity of the DFB semiconductor laser and the key parameter of the drive current cooperative random filtering module; the random filtering module is a random filtering module based on Liquid Crystal On Silicon (LCOS), a random filtering module based on FP interferometer or a random filtering module based on Mach-Zehnder interferometer, and the key space of the random filtering module is a^mWherein a is the number of wavelets of the wavelength, and m is the number of regulation and control codes for each wavelet intensity; the random filtering module based on the FP interferometer comprises a plurality of FP cavities which are connected in a cascading mode.

Further, the number of FP cavities is not less than 2.

In conclusion, the invention has the following beneficial effects:

the chaotic communication transceiver provided by the invention can realize the random selection function of a light path range after spectrum coding by using the random filtering module to replace the traditional feedback mirror, the random filtering module can randomly select and switch wavelets with a wavelengths, and the intensity of each wavelet can be regulated and controlled to be m, so that a can be realized^mThe key space of the chaotic optical communication transceiving system is remarkably improved by combining the key parameters of the DFB laser; by combining the characteristic parameters of the random filtering module with the key parameters of the DFB laser, the special hardware encryption advantage of chaotic secret communication is exerted, and the communication safety is ensured; the random filtering module is adopted for random filtering feedback, so that the time delay characteristic is effectively hidden, the communication structure is simple, and the robustness of communication is ensured; the random filtering module of the chaotic communication transceiver can be manufactured by using the same hardware parameters, the consistency of hardware is ensured, chaotic synchronization is easy to realize, and the chaotic communication transceiver is convenient for large-scale production.

Drawings

FIG. 1 is a block diagram of the present invention;

FIG. 2 is a schematic diagram of the present invention applied to a large-key space chaotic secure communication system.

In the figure: 1-a first DFB semiconductor laser, 2-a beam splitter, 3-a coupler, 4-a random filtering module, 5-a first polarization controller, 6-a second DFB semiconductor laser, 7-a Mach-Zehnder modulator, 8-a second polarization controller, 9-a first coupler, 10-an optical isolator, 11-an optical fiber ring, 12-a second coupler, 13-a third polarization controller, 14-a first photodetector, 15-a second photodetector, 16-a signal demodulation operation system, 17-a signal output display device, an I-chaotic optical communication transmitter, an II-chaotic optical communication receiver, 21-a beam splitter first input/output end, 22-a beam splitter second input/output end, 31-a coupler first input/output end, 32-coupler output, 33-coupler input.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings.

As shown in fig. 1, a large-key space chaotic optical communication transceiver includes a DFB semiconductor laser 1, a beam splitter 2, a coupler 3, and a random filtering module 4 serving as a feedback mirror to realize a random selection function after optical path range encodes a spectrum, a first input/output end 21 of the beam splitter 2 receives laser generated by the first DFB semiconductor laser 1, a second input/output end 22 of the beam splitter 2 is connected to a first input/output end 31 of the coupler 3, an output end 32 of the coupler 3 is connected to an input end of the random filtering module 4, and an output end of the random filtering module 4 is connected to an input end 33 of the coupler 3; the beam splitter 2 and the input and output ends of the coupler 3 complete bidirectional transmission at the same connecting end, and belongs to the technology available to those skilled in the art; the chaotic signal is fed back to the DFB semiconductor laser 1 through the coupler 3 and the beam splitter 2, the communication transmitter I generates a chaotic carrier, the communication receiver II generates a chaotic carrier synchronization signal, and the chaotic carrier is output through the beam splitter 2; the key space of the chaotic optical communication transceiver is formed by the feedback intensity of the DFB semiconductor laser 1 and the key parameter of the drive current cooperated with the random filtering module 4.

The random filtering module 4 is a random filtering module based on a silicon-based liquid crystal, or a random filtering module based on an FP interferometer, or a random filtering module based on a Mach-Zehnder interferometer, an input signal of the random filtering module based on the silicon-based liquid crystal is dispersed through a traditional grating and then passes through a silicon-based liquid crystal optical processor, the silicon-based liquid crystal optical processor comprises a reflection liquid crystal element matrix, voltage is applied through a reflection liquid crystal matrix element to shift the phase of a reflection signal, the signal beam component reaches the silicon-based liquid crystal processor, and the wavelength is selected randomly; because the wavelength is separated in the silicon-based liquid crystal processor, the control of each wavelength is independent of all other wavelengths, and the switching or filtering can be carried out under the condition of not interfering other wavelengths, the random filtering module based on the track liquid crystal can use the existing instrument, the model is WS-04000A-C-S-1-AA-00, the working wavelength range is 1526 nm-1568.7 nm, and the tunable bandwidth is 10GHz-5.36 THz.

The random filtering module based on the FP interferometer comprises a plurality of FP cavities which are connected in a cascade mode, the number of the FP cavities is not less than 2, and each FP cavity is divided into two partsEach FP cavity comprises two parallel wedge-shaped reflectors, an air gap between the wedge-shaped reflectors contains an optical waveguide, 2 FP cavities are selected and cascaded in the embodiment to form a random filtering module, and the FP cavities output optical frequencyf=mc/2μlWhereinmIs an interference order,μIs a refractive index,lThe cavity length and the C are the light speed, the frequency of output light is controlled by controlling the cavity length and the refractive index of the FP cavity, and further random filtering is realized, wherein the refractive index of the FP cavity can be controlled by voltage, and the working wavelength C waveband can be realized by using a Fabry-Perot type optical filter in the prior art and the like.

An input optical signal of a random filtering module based on a Mach-Zehnder interferometer is divided into two optical signals with equal intensity through a coupler, the two optical signals are transmitted in two interference arms with unequal lengths of the Mach-Zehnder interferometer to generate a certain optical path difference, and superposition interference is carried out in the other coupler, so that optical output with different wavelengths is realized, and the filtering range and precision are improved. The random filtering module based on the Mach-Zehnder interferometer can be realized by using a Mach-Zehnder type optical filter or a Mach-Zehnder filter based on a cascade long-period fiber grating and the like in the prior art, and the working wavelength is C wave band.

As shown in fig. 2, the chaotic secret communication system of the invention can be used as a chaotic optical transmitter and a chaotic optical receiver, the structures of the chaotic optical transmitter and the chaotic optical receiver are the same, and a chaotic carrier generated by a chaotic optical communication transmitter i through random filtering feedback is transmitted through a polarization controller 5; laser generated by the second DFB semiconductor laser 6 is modulated by the mach-zehnder modulator 7 into a data signal to be transmitted, and then transmitted by the second polarization controller 8; the data signal to be transmitted and the chaotic carrier signal enter the first coupler 9 at the same time, and form a transmitting signal through the coupling of the first coupler 9, so that the hiding of the transmission information is realized; the hidden information enters the optical fiber ring 11 for transmission through the optical isolator 10, and the hidden information transmitted to the receiver enters the second photoelectric detector 15 after passing through the second coupler 12 to be reserved; the same chaotic carrier synchronization signal generated by the chaotic optical communication receiver ii enters the first photodetector 14 through the third polarization controller 13, the transmission signal of the hidden information and the chaotic carrier synchronization signal are detected by the second photodetector 15 and the first photodetector 14, and then are subjected to difference operation by the signal demodulation operation system 16 to demodulate data information to be transmitted, and the demodulated data signal to be transmitted is displayed by the signal output display device 17.

The random filtering module 4 selects a random filtering module based on the liquid crystal on silicon to form a chaotic optical communication transmitter and a chaotic optical communication receiver, and the feedback intensity and the driving current of the DFB laser and the adjustable line width of the random filtering module based on the liquid crystal on silicon can be used as key parameters. For example, the adjustable range of the feedback intensity of the DFB laser is 0.2-0.3, the adjustment precision is 0.01, and the key space is 10; the adjustable range of the driving current of the DFB laser is 18-20mA, the adjustment precision is 0.1mA, and the key space is 20; the adjustable line width adjusting range of the LCOS-based random filter module is 10GHz-5.36THz, the adjusting precision is 125GHz, the key space is 42, the intensity of each line width sub-wave can be adjusted and coded, if the coding is 0, 1, namely m =2 (m =2 can be coded actually), and the key space is 2, the key space of the LCOS-based random filter module is 1764 (42)²) (ii) a Therefore, when the strength code of the expected sub-wave is 2, the sum of the key space of the chaotic transceiver consisting of the random filtering module based on the liquid crystal on silicon is 200¹⁷⁶⁴。

The random filtering module 4 selects a chaotic transmitter and a chaotic receiver which are formed by a random filtering module based on an FP interferometer, and the cavity length and the refractive index of an FP cavity can be used as key parameters, such as: fixing the cavity lengths of two mirror surfaces of the FP cavity, tuning the waveguide refractive index of the FP cavity by controlling bias voltage, wherein the tuning range is 6.7-7.2V, the adjusting precision is 0.05V, the key space is 10, and the number of cascaded FP cavities is minimum, namely the key space of the cascaded 2 FP cavities is 20; similarly, the intensity of each line width wavelet can regulate and control the coding, and assuming that the coding is 0, 1, i.e. m =2, and the key space is 2, the key space of the FP interferometer-based random filtering module is 400 (20)²) In actual operation, the number m of codes is more than or equal to 2, and the key space is far larger than a theoretical value calculated according to the minimum value; similarly, 2 DFB lasers are expected to be cascaded by combining the key space of the DFB lasersThe sum of the key spaces of the random filtering modules of the FP cavity is 200⁴⁰⁰。

The random filtering module 4 selects a chaotic transmitter and a chaotic receiver of the random filtering module based on the Mach-Zehnder interferometer, for example: the wavelength tuning range of the Mach-Zehnder interferometer is 0.5nm-44.5nm, the adjusting precision is 2nm, and the key space is 22; similarly, the intensity of each line width wavelet can be controlled and coded, and if the code is 0, 1, namely m =2 (m is larger than or equal to 2 can be coded actually), and the key space is 2, the key space of the random filtering module based on the Mach-Zehnder interferometer is 484 (22)²) (ii) a Similarly, in combination with the key space of the DFB laser itself, the key space of the random filtering module based on the Mach-Zehnder interferometer is expected to add up to 200⁴⁸⁴。

The random filtering module effectively hides the time delay characteristic, has simple communication structure, ensures the robustness of communication, can effectively improve the key space of the chaotic light communication receiving and transmitting system, exerts the special hardware encryption advantage of chaotic secret communication and ensures the safety of communication.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.

Claims

1. A large-key space chaotic optical communication transceiver comprises a DFB semiconductor laser (1), a beam splitter (2) and a coupler (3), and is characterized in that: the random selection optical fiber laser also comprises a random filtering module (4) which is used as a feedback mirror to realize the random selection function of the optical path range after the optical spectrum is coded, a first input and output end (21) of the beam splitter (2) receives laser generated by the first DFB semiconductor laser (1), a second input and output end (22) of the beam splitter (2) is connected with a first input and output end (31) of the coupler (3), an output end (32) of the coupler (3) is connected with the input end of the random filtering module (4), and the output end of the random filtering module (4) is connected with the input end (33) of the coupler (3); the key space of the chaotic optical communication transceiver is formed by the feedback intensity of the DFB semiconductor laser (1) and the key parameter of the drive current cooperative random filtering module (4);

the random filtering module (4) is a silicon-based liquid crystal random filtering module or a FP interferometer random filtering module or a Mach-Zehnder interferometer random filtering module, and the key space of the random filtering module (4) is a^mWherein a is the number of wavelets of the wavelength, and m is the number of regulation and control codes for each wavelet intensity; the random filtering module based on the FP interferometer comprises a plurality of FP cavities which are connected in a cascading mode.

2. The large-key spatial chaotic optical communication transceiver of claim 1, wherein: the number of FP cavities is not less than 2.