CN112511225B - Polarization modulation indoor wireless optical communication system front-end structure and system - Google Patents

Polarization modulation indoor wireless optical communication system front-end structure and system Download PDF

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CN112511225B
CN112511225B CN202011168185.9A CN202011168185A CN112511225B CN 112511225 B CN112511225 B CN 112511225B CN 202011168185 A CN202011168185 A CN 202011168185A CN 112511225 B CN112511225 B CN 112511225B
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邵理阳
王国庆
肖冬瑞
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Southern University of Science and Technology
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
    • H04B10/114—Indoor or close-range type systems
    • H04B10/1149—Arrangements for indoor wireless networking of information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/25—Arrangements specific to fibre transmission
    • H04B10/2575—Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/29—Repeaters
    • H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
    • H04B10/2912—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form characterised by the medium used for amplification or processing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/501—Structural aspects
    • H04B10/503—Laser transmitters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/516—Details of coding or modulation
    • H04B10/54—Intensity modulation

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Abstract

The invention relates to a polarization modulated indoor wireless optical communication system front end structure and a system, wherein the front end structure comprises: the polarization modulator is used for receiving the optical signal after passing through the polarization controller at a first end, receiving an electric signal for modulating the optical signal at a second end and outputting the modulated optical signal at a third end; the optical amplifier is used for amplifying the modulated optical signal; and the inclined fiber grating TFG is used for carrying out intensity modulation on the optical signal output by the optical amplifier and realizing light emission and space light diffraction of the indoor space. The indoor wireless optical communication system solves the technical problem that the signal is unstable due to polarization voltage drift caused by intensity modulation of the existing optical signal.

Description

Polarization modulation indoor wireless optical communication system front-end structure and system
Technical Field
The invention relates to the technical field of optical communication, in particular to a front-end structure and a front-end system of a polarization-modulated indoor wireless optical communication system.
Background
The space optical communication technology has the advantages of high transmission speed, large communication capacity, electromagnetic interference resistance, good confidentiality, high stability, low cost and the like, does not need to lay optical fibers, and obtains wide attention and research in communication application.
In the field of conventional spatial optical communication, intensity modulation is generally used for signal modulation, and most commonly, a mach-zehnder (MZ) -based intensity modulator (MZM) is used, but the MZ-based intensity modulator needs to load a bias voltage to maintain stable intensity modulation. However, since the MZ-based intensity modulator is affected by temperature, vibration, and the like during operation, the bias voltage thereof cannot be kept stable, and thus stable intensity modulation of the communication signal cannot be realized.
How to realize stable modulation of communication signals in an optical communication system is a technical problem which needs to be solved at present.
Disclosure of Invention
Technical problem to be solved
In view of the above drawbacks and deficiencies of the prior art, the present invention provides a front end structure and a system of a polarization-modulated indoor wireless optical communication system, which solve the technical problem of signal instability caused by polarization voltage drift due to intensity modulation of an existing optical signal.
(II) technical scheme
In order to achieve the purpose, the invention adopts the main technical scheme that:
in a first aspect, an embodiment of the present invention provides a polarization-modulated front-end structure of an indoor wireless optical communication system, including:
the polarization modulator is used for receiving the optical signal after passing through the polarization controller at a first end, receiving an electric signal for modulating the optical signal at a second end and outputting the modulated optical signal at a third end;
the optical amplifier is used for amplifying the modulated optical signal;
and the inclined fiber grating TFG is used for carrying out intensity modulation on the optical signal output by the optical amplifier and realizing light emission and space light diffraction of the indoor space.
Optionally, the front end structure further comprises: the laser generating module is used for generating optical signals, and the polarization controller is used for carrying out polarization control on the laser of the laser generating module;
the first end of the polarization controller is communicated with the laser generation module, and the second end of the polarization controller is communicated with the polarization modulator.
Optionally, the optical signal input to the polarization modulator comprises a laser optical signal in the near infrared band.
Optionally, the optical signal received by the first end of the polarization modulator is: l is0(A1，p)，A1Is the amplitude value of the optical signal, and p is the polarization state of the optical signal;
the electrical signal received by the second terminal of the polarization modulator is:
Figure BDA0002746425150000021
A2is the amplitude value of the electrical signal, f is the frequency of the electrical signal,
Figure BDA0002746425150000022
is the initial phase of the electrical signal;
then, the third terminal of the polarization modulator outputs the modulated optical signal
Figure BDA0002746425150000023
Figure BDA0002746425150000024
Comprises the following steps:
Figure BDA0002746425150000025
A3as amplitude value of the optical signal, A3As a function of time t. Under polarization modulation, A3＝A2(t), f is the frequency of the electrical signal,
Figure BDA0002746425150000026
p is the polarization state of the output optical signal from the polarization modulator for the initial phase of the electrical signal.
Optionally, the tilted fiber grating TFG input optical signal is
Figure BDA0002746425150000031
Optical signal output by tilted fiber grating TFG
Figure BDA0002746425150000032
Comprises the following steps:
Figure BDA0002746425150000033
A5the amplitude value of the output optical signal for the TFG, f the frequency of the electrical signal,
Figure BDA0002746425150000034
p is the polarization state of the output optical signal of the TFG, and β is the coefficient, which is the initial phase of the electrical signal.
Optionally, the spatial light diffraction angle α of the tilted fiber grating TFG is:
Figure BDA0002746425150000035
wherein n is the refractive index of the fiber core in the TFG, theta is the inclination angle of the TFG, lambda is the period of the TFG, and lambda is the wavelength of the optical signal transmitted in the TFG;
the angular dispersion D is:
Figure BDA0002746425150000036
alternatively, when the TFG has the largest angular dispersion value, θ is 45 °.
In a second aspect, an embodiment of the present invention further provides a polarization-modulated indoor wireless optical communication system, including a detection structure and any one of the aforementioned front-end structures of the indoor wireless optical communication system; the detection structure detects the optical information of the indoor space and converts and analyzes the detected optical information.
(III) advantageous effects
The invention has the beneficial effects that: the polarization modulation indoor wireless optical communication system front-end structure adopts a polarization modulation mode, does not need bias voltage, and further solves the problem of unstable signals.
In addition, the front end structure of the invention adopts low-cost inclined fiber gratings based on optical fibers, and the optical fibers realize high-stability intensity modulation through polarization modulation, realize high-efficiency integrated space light emitters and realize diffraction beam angle adjustment of space light. And then solved the unstable problem of signal in traditional intensity modulation.
Drawings
Fig. 1 is a schematic diagram of a front-end structure of an indoor space optical communication system based on polarization modulation according to the present application;
fig. 2 is a schematic structural diagram of an indoor space optical communication system based on polarization modulation according to the present application;
FIG. 3 is a diagram of the process of light propagation analysis in the present application at 45 ° TFG;
fig. 4 is a schematic diagram of a test result of the indoor space optical communication system according to the present application.
Detailed Description
In order to better understand the above technical solutions, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
Example one
As shown in fig. 1, fig. 1 is a schematic diagram illustrating a front-end structure of an indoor space optical communication system based on polarization modulation according to an embodiment of the present application;
the indoor wireless optical communication system front end structure of this embodiment includes: the device comprises a laser generation module, a polarization controller, a polarization modulator, an optical amplifier and a TFG;
the laser generation module of this embodiment may be a tunable laser, that is, a tunable laser, and the laser wavelength is in the near-infrared band and can be adjusted.
The polarization controller is used for carrying out polarization control on the laser of the laser generation module, for example, controlling the polarization state of an optical signal of the laser signal in the transmission process; the first end of the polarization controller is communicated with the laser generation module, and the second end of the polarization controller is communicated with the polarization modulator;
the polarization modulator is used for receiving the optical signal after passing through the polarization controller at a first end, receiving an electric signal for modulating the optical signal at a second end and outputting the modulated optical signal at a third end; in the embodiment, a high-speed polarization modulator and a high-speed random signal generator are adopted, and the high-speed polarization modulator is modulated by a high-speed random signal generated by the high-speed random signal generator, so that the high-speed polarization modulation of an optical signal is realized;
the optical amplifier is used for amplifying the modulated optical signal; in this embodiment, the optical amplifier based on the erbium-doped fiber is adopted, so that a weak optical signal can be amplified by one hundred times.
And the inclined fiber grating (TFG) is used for carrying out intensity modulation on the optical signal output by the optical amplifier and realizing light emission and spatial light diffraction of the indoor space.
In this embodiment, the optical signal input to the polarization modulator includes a laser optical signal in the near-infrared band.
It should be noted that the optical signal received by the first end of the polarization modulator is: l is0(A1，p)，A1Is the amplitude value of the optical signal, and p is the polarization state of the optical signal;
the electrical signal received by the second terminal of the polarization modulator is:
Figure BDA0002746425150000051
A2is the amplitude value of the electrical signal, f is the frequency of the electrical signal,
Figure BDA0002746425150000052
is the initial phase of the electrical signal;
then, the third terminal of the polarization modulator outputs the modulated optical signal
Figure BDA0002746425150000053
Figure BDA0002746425150000054
Comprises the following steps:
Figure BDA0002746425150000055
A3as amplitude value of the optical signal, A3As a function of time t. Under polarization modulation, A3＝A2(t) of (d). Under conventional intensity modulation, A3＝A2(t) Δ a, where Δ a is the amplitude change caused by the change in bias voltage in the intensity modulation.
Figure BDA0002746425150000061
P in (1) is the polarization state of the output optical signal of the polarization modulator, f is the frequency of the electrical signal,
Figure BDA0002746425150000062
is the initial phase of the electrical signal.
In this embodiment, the tilted fiber grating TFG input optical signal is
Figure BDA0002746425150000063
Figure BDA0002746425150000064
Optical signal output by tilted fiber grating TFG
Figure BDA0002746425150000065
Comprises the following steps:
Figure BDA0002746425150000066
A5the amplitude value of the output optical signal for the TFG, f the frequency of the electrical signal,
Figure BDA0002746425150000067
p is the polarization state of the output optical signal of the TFG, and β is the coefficient, which is the initial phase of the electrical signal.
Further, the spatial light diffraction angle α of the tilted fiber grating TFG is:
Figure BDA0002746425150000068
wherein n is the refractive index of the fiber core in the TFG, theta is the inclination angle of the TFG, lambda is the period of the TFG, and lambda is the wavelength of the optical signal transmitted in the TFG;
the angular dispersion D is:
Figure BDA0002746425150000069
when TFG has the largest angular dispersion value, θ is 45 °.
When the invention is used, the optical signal L3After spatial transmission, the signal is finally received by a photoelectric detector and demodulated. The amplitude of the finally demodulated signal is A6。
Using a polarization modulation scheme, the optical signal L3Amplitude value A of5After being demodulated, the signal will not generate the change of the value, namely, the value is still A6＝A4(t)＝A5，A6＝A5I.e. a stable transmission of the signal is achieved. When a conventional intensity modulation scheme is employed, the optical signal L3Amplitude value A of5After demodulation, the signal amplitude value changes, i.e. A6＝A4(t)*ΔA＝A5Δ a. At this time A6≠A5Distortion is generated in the transmission process of the signal.
The front-end structure of this embodiment has adopted the mode of polarization modulation, need not bias voltage, and then has solved the unstable problem of signal.
In addition, the front end structure of the invention adopts low-cost inclined fiber gratings based on optical fibers, and the optical fibers realize high-stability intensity modulation through polarization modulation, realize high-efficiency integrated space light emitters and realize diffraction beam angle adjustment of space light. And then solved the unstable problem of signal in traditional intensity modulation.
Example two
An indoor wireless communication system according to an embodiment of the present invention is described with reference to fig. 3 and 4, where fig. 3(a) is a propagation diagram of light in a 45 ° TFG in the present application, and fig. 3(b) is a side structure diagram of an optical signal transmitted in the 45 ° TFG, when an input optical signal propagates in a core, only s-waves in polarization state will be side-diffracted to the outside of an optical fiber through a cladding layer, and the remaining p-waves in polarization state will be transmitted through the 45 ° TFG through a forward core.
In the present embodiment, the 45 ° TFG has the largest angular dispersion, and optical signals with different wavelengths will have different transmission angles in spatial transmission, as shown in fig. 3 (a).
In fig. 3(b), when light is transmitted in a 45 ° TFG, which shows the end-face divergence, the angle of light from the core to the cladding to the outside of the fiber tends to diverge, thus requiring a cylindrical lens to collimate the light in the horizontal direction.
Fig. 3(c) shows a wave mode matching plot for a 45 ° TFG, where K is the wave vector of the incident light, K is 2n pi/λ, n is the refractive index of the core, and λ is the wavelength of the incident light. KGIs the wavevector, K, of the 45 DEG TFGG＝2nπ/Λ，KGCan be divided into a horizontal component and a vertical component, respectively KXAnd Kγ，KRExpressed as the wave vector of the s-wave. The relationship between the wave vectors is shown in fig. 1 (c). Their relationship is:
Figure BDA0002746425150000081
fig. 2 is a schematic structural diagram of an indoor space optical communication system according to the present invention, and an indoor space optical communication system based on polarization control with low cost and high stability is explained based on the schematic structural diagram, and the main steps are as follows:
(1) laser signal modulation step
The existing optical communication system adopts direct intensity modulation, and has the defect that direct voltage bias control is required when intensity modulation is adopted, and under the influence of environmental regulation such as temperature change, vibration and the like, direct voltage bias can change under the actual condition, so that the intensity modulation is unstable, the signal intensity is unstable, and the stability of the optical communication system is influenced.
In the embodiment, a polarization modulation-based mode is adopted, so that the problem of unstable signal intensity under intensity modulation in the traditional space optical communication system is solved. As shown in FIG. 2, the laser signal emitted by the tunable laser is a continuously tunable wavelength signal and the emitted light signal is
Figure BDA0002746425150000082
Wherein A, p, λ and
Figure BDA0002746425150000083
the amplitude value, polarization state, wavelength and initial phase of the optical signal. Optical signal L0After passing through the polarization controller and the polarization modulator, the polarization state thereof becomes p1The signal generator generates a signal having a frequency f and an amplitude A0And an initial phase of
Figure BDA0002746425150000085
The electrical signal E is applied to the optical signal through the polarization modulator, and the modulated optical signal (including effective communication information) is:
Figure BDA0002746425150000084
in this step, it is noted that the polarization modulation is generated for the optical signal at this time, but no change in the intensity value of the optical signal is achieved at this time.
In addition, after the optical signal is subjected to the above polarization modulation, after the optical signal passes through the polarization sensitive optical device, in this embodiment, the optical signal is a 45 ° TFG (the tilted grating structure destroys the internal symmetric structure thereof, so that the optical signal has the polarization sensitive characteristic), the polarization orthogonal component of the optical signal is not balanced any more, and the intensity amplitude thereof changes with the polarization state.
Namely, the 45-degree TFG is an online polarizer, and the polarized light signal realizes the conversion from linear polarization modulation to intensity modulation through the TFG. Polarization modulated optical signal
Figure BDA0002746425150000091
With polarization-converted intensity-modulated optical signals
Figure BDA0002746425150000092
The relationship (beta is a coefficient):
Figure BDA0002746425150000093
in the embodiment, the light emitting device based on the 45-degree TFG is used as a space light emitter and a space light diffraction device at the same time, so that high-efficiency light emission and light beam angle adjustment are realized. After the light with different wavelengths passes through the 45-degree TFG, the side surface diffraction characteristics are generated, namely, the light with different wavelengths respectively has different spatial diffraction angles after being diffracted from the 45-degree TFG side surface.
Specifically, the spatial light angle diffraction is expressed by the angular dispersion D, i.e. the divergence of the tilt angle of the TFG with wavelength is shown, which is expressed as
Figure BDA0002746425150000094
Where n is the refractive index of the fiber core, θ is the tilt angle of the TFG, Λ is the period of the TFG, and λ is the wavelength of the optical signal transmitted at the TFG. When θ is 45 degrees, the angular dispersion is the largest, i.e., the divergence of different wavelengths in different directions is also the largest.
When optical signals with different wavelengths pass through the 45 DEG TFG and propagate into free space, the light with different wavelengths is received by the photoelectric detector after passing through different paths.
The optical communication system shown in fig. 2 may include a detection structure that may include a plurality of Photodetectors (PDs), an oscilloscope, and a computer, i.e., a host computer.
After the modulated space optical signal is received by a space Photoelectric Detector (PD), the intensity information is demodulated and recovered through data acquisition, and further the indoor space optical communication of low-cost polarization control is realized.
When the invention is used, the optical signal L3After spatial transmission, the signal is finally received by a photoelectric detector and demodulatedAnd (5) preparing. The amplitude of the finally demodulated signal is A6。
Using a polarization modulation scheme, the optical signal L3Amplitude value A of5After being demodulated, the signal will not generate the change of the value, namely, the value is still A6＝A4(t)＝A5，A6＝A5I.e. a stable transmission of the signal is achieved. When a conventional intensity modulation scheme is employed, the optical signal L3Amplitude value A of5After demodulation, the signal amplitude value changes, i.e. A6＝A4(t)*ΔA＝A5Δ a. At this time A6≠A5Distortion is generated in the transmission process of the signal.
In order to better demonstrate the signal stability of the optical communication system according to the embodiment of the present invention, the existing system and the system according to the embodiment of the present invention were tested, as shown in fig. 4. Fig. 4(a) is an electrical signal loaded on an optical carrier. The line corresponding to 0 minute in fig. 4(b) is the electrical signal demodulated in the optical communication system shown in fig. 2, and the line corresponding to 30 minutes in fig. 4(b) is the electrical signal demodulated in the optical communication system shown in fig. 2 after the optical communication system of the embodiment of the present invention operates for 30 minutes.
It can be seen from the results that the intensity of the electrical signal of the system after polarization modulation maintains a high degree of consistency, i.e. the demodulation system maintains a certain stability after working for a certain time. The line corresponding to 0 minute in fig. 4(c) is the electrical signal demodulated in the system shown in fig. 2, and the line corresponding to 30 minutes in fig. 4(c) is the electrical signal demodulated after the system shown in fig. 2 is operated for 30 minutes.
EXAMPLE III
The optical communication system of the embodiment of the invention comprises: the laser generation module can adopt an adjustable laser light source with low cost; the system comprises a polarization controller, a polarization modulator, a random signal generator, an optical amplifier, a TFG and a detection structure;
the probe structure may include: the device comprises a laser receiving module and a signal processing module;
the laser receiving module can adopt a space light detector to realize space light receiving and high-speed photoelectric conversion; and the signal processing module is used for carrying out data processing on the acquired optical signals and realizing space optical communication.
The embodiment of the invention combines the polarization characteristic, the light emission characteristic and the light diffraction characteristic of the on-line inclined grating, reduces the system volume, improves the system energy utilization rate, creatively utilizes the polarization characteristic, and solves the problem of unstable signals during intensity modulation in the traditional space optical communication system.
The TFG in the front-end structure adopts an inclined fiber grating based on optical fibers, and realizes space light emission by utilizing the side light diffraction characteristic of the inclined fiber grating to diffract light in the optical fibers in a side diffraction mode; meanwhile, the characteristic of high polarization sensitivity of the high-speed signal is utilized to realize the one-to-one conversion of polarization modulation and intensity modulation, so that the high-stability intensity modulation of the high-speed signal is completed.
It should be noted that in the description of the present specification, the description of the term "one embodiment", "some embodiments", "examples", "specific examples" or "some examples", etc., means that a specific feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, the claims should be construed to include preferred embodiments and all changes and modifications that fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention should also include such modifications and variations.

Claims (8)

1. A polarization modulated indoor wireless optical communication system front end structure, comprising:
the polarization modulator is used for receiving the optical signal after passing through the polarization controller at a first end, receiving an electric signal for modulating the optical signal at a second end and outputting the modulated optical signal at a third end;
the optical amplifier is used for amplifying the modulated optical signal;
the inclined fiber grating TFG is used for carrying out intensity modulation on an optical signal output by the optical amplifier and realizing light emission and space light diffraction of an indoor space;
the spatial light diffraction angle α of the tilted fiber grating TFG is:
Figure FDA0003180539650000011
wherein n is the refractive index of the fiber core in the TFG, theta is the inclination angle of the TFG, lambda is the period of the TFG, and lambda is the wavelength of the optical signal transmitted in the TFG;
the angular dispersion D is:
Figure FDA0003180539650000012
2. the front-end structure of claim 1, further comprising: the laser generating module is used for generating optical signals, and the polarization controller is used for carrying out polarization control on the laser of the laser generating module;
the first end of the polarization controller is communicated with the laser generation module, and the second end of the polarization controller is communicated with the polarization modulator.
3. The front-end architecture of claim 1, wherein the optical signal input to the polarization modulator comprises a laser optical signal in the near-infrared band.
4. The front-end structure of claim 1,
the optical signal received by the first end of the polarization modulator is: l is0(A1，p)，A1Is the amplitude value of the optical signal, and p is the polarization state of the optical signal;
the electrical signal received by the second terminal of the polarization modulator is:
Figure FDA0003180539650000021
A2is the amplitude value of the electrical signal, f is the frequency of the electrical signal,
Figure FDA0003180539650000022
is the initial phase of the electrical signal;
the third end of the polarization modulator outputs the modulated optical signal
Figure FDA0003180539650000023
Comprises the following steps:
Figure FDA0003180539650000024
A3is an amplitude value of the optical signal, and A3As a function of time t; under polarization modulation, A3＝A2(t)。
5. Front end structure according to any one of claims 1 to 4,
the tilted fiber grating TFG input optical signal is
Figure FDA0003180539650000025
Optical signal output by tilted fiber grating TFG
Figure FDA0003180539650000026
Comprises the following steps:
Figure FDA0003180539650000027
A5the amplitude value of the output optical signal for the TFG, f the frequency of the electrical signal,
Figure FDA0003180539650000028
p is the polarization state of the output optical signal of the TFG, and β is the coefficient, which is the initial phase of the electrical signal.
6. The front-end structure of claim 1, wherein θ is 45 ° when TFG has the largest angular dispersion value.
7. The front-end architecture of any one of claims 1 to 4, wherein the polarization modulator is a high-speed polarization modulator, and the second end of the high-speed polarization modulator receives a high-speed random signal to modulate the high-speed polarization modulator.
8. A polarization modulated indoor wireless optical communication system, comprising a probe structure, further comprising: the indoor wireless optical communication system front-end architecture of any one of claims 1 to 7; the detection structure detects the optical information of the indoor space and converts and analyzes the detected optical information.
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