# Wireless Radio Frequency Automation of Intelligent Optical Fiber Transmission System Based on the Differential Evolution Method

Authors: Lei Jin; Jinghong Zhao; Xing Huang; Bin Lu
Journal: Advances in Multimedia
 (2021)

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## Abstract

With the continuous development and improvement of science and technology, optical fiber transmission has been transformed from traditional manual transmission to automatic transmission, and the transmission efficiency is constantly improving. In order to further analyze the performance of the intelligent optical fiber transmission process, the differential evolution analysis method is introduced in this paper, integrated architecture is built through the integrated optical and intelligent optical fiber, and the corresponding vector signal error value is solved through the comparison of transmission schemes. The error value is about 9%, through simulation experiments, which can effectively meet the requirement of automation of the wireless radio frequency of the intelligent optical fiber transmission system and realize long-distance transmission.


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## Body

## 1. Introduction

With the continuous development of social economy, there has been a full development in both hardware and software for data transmission, for example, from the perspective of hardware, the latest technologies such as smart optical fiber and software technologies such as radio frequency technology, while the content of transmission has also changed from the most primitive data, images, voice, and video to diverse multimedia [1–3]. In terms of the current transmission hardware, for example, copper wire can be used to meet the transmission and corresponding capacity of communication [4–6]; solutions such as high reliability, fast transmission, and low cost can be realized. Compared with traditional access methods, the smart optical fiber access can be used for a lower maintenance cost and a lower update frequency [7, 8]. Meanwhile, due to the physical characteristics of optical fiber, the communication transmission distance covered by it is also longer.The so-called wireless radio frequency transmission uses light as the relevant carrier and converts the photoelectric data into the radio frequency signal in the transmission bandwidth signal in the optical fiber. This is a new type of transmission method with low cost, low loss, and long transmission distance. Such transmission mode has gradually become the main method of communication transmission. According to the technical content, wireless radio frequency transmission can be divided into two types: analog and digital [9, 10].For wireless communication or light communication, the processing, transmission, and management of information cannot be completed alone [11]. Therefore, in view of these shortcomings, key technical support is performed for the network fusion process on the basis of the fusion of optical fiber communication and wireless communication fusion relying on the differential evolution method; radio frequency automation is introduced and evaluated, aiming to lay a theory for communication base.


## 2. Intelligent Optical Fiber Network Construction

The intelligent optical fiber network mainly includes two parts: optical fiber access and wireless access. The wireless access mainly implements voice services through the 5G network. For optical fiber access, in the entire network architecture, all users share a single optical signal. The signal is distributed through the light source signal, but because multiple terminal users share the entire wavelength, the cost is also reduced and maintenance is facilitated [12].The mathematical model for the intelligent optical fiber network construction is shown in Figure1. The transmitter of the vector signal first generates the corresponding signal and meanwhile outputs the corresponding signal-to-noise ratio index to express the quantitative calculation and calibration of the vector signal generator’s noise and signal.Figure 1
Mathematical model of digital ROF system.


### 2.1. VSG

The system sampling frequency/s depends on the sum of the maximum and minimum frequencies of the RF signalxi,tj=xminj+rand0,1∗xmaxj−xminj and ⇒. The conditions for no aliasing during the sampling process are as follows: vi,tj, where xi,tj, and the function ui,tj represents the largest integer not greater than x. When the symbol rate is xi,tj,vi,tj, the complex amplitude of the QAM signal can be obtained by the following formula:(1)st=Re∑ibt−iTAiejφiAejωcx.Among them,⇒, fui,t<fxi,t, xi,t⟵ui,t. fxi,t<fΔ, and Δ⟵xi,t are the amplitude and phase of the i-th character, respectively, b(t) is the signal pulse of unit amplitude, A is the amplitude of the RF carrier, T is the character duration, xi,t⟵xi,t is the angular frequency of the carrier. The frequency response of the pulse shaping filter can be obtained by the following formula:(2)Gf=1,f<fN1−α,12+12sinπ2fNfN−fα,fN1−α≤f≤fN1+α,0,f>fN1+α.In the formula,fN=1/2T WiMAX standard RF carrier frequency fc = 2.475 GHz, the bandwidth is 20 MHz, and the guard band bandwidth on both sides is 15 MHz each, so the total bandwidth of the RF carrier is 50 MHz. nz (3): the value range of nz is 1∼50. In this paper, nz=40, the sampling frequency is fs = 125MS/s. The band-pass signal is sampled out of band, and noise will enter the Nyquist area. The description of the band-pass signal noise is based on the assumption that both VSG in-band and out-of-band noise come from thermal noise. Thermal noise is a Gaussian process with a mean value of 0. The noise power PN=nzfsN0, where N0=kT/2, the VSG output signal-to-noise ratio can be calculated by the following formula:(3)SNRVSG=10lgPSPN=10lgPSnzfsN0.


### 2.2. ADC

Aperture and clock jitter will reduce the signal-to-noise ratio of the ADC. The jitter noise is approximately a Gaussian process with a mean value of 0. Assuming the input signalst=s0sin2πfct, the signal change rate ds/dt=2πfcs0cos2πfct, amplitude value is divided by 2 to get the root mean square value of ds/dt: ds/dtrms=2πfcs0/2/42. Let Δsrms be the root mean square noise, Δt is the standard deviation σjn,ADC of the root mean square jitter, and substituting it into the above formula to obtain Δsrms/σjn,ADC=2πfcs0/2, so that the root mean square noise obtained by the ADC is Δsrms=2πfcs0σjn,ADC/2. The root mean square value of the full-scale input sine wave is s0/2. Therefore, the ratio of the rms signal to the rms noise is calculated to obtain the signal-to-noise ratio between ADC noise and signal [13], as shown in the following formula:(4)SNRjn,ADC=−20lgΔsrmss0/2=−20lg2πfcσjn,ADC.Different from jitter noise, there is still quantization noise in the binary digital output of ADC, and it is related to the influence on the signal-to-noise ratio and carrier factor [14]. The specific calculation is shown in the following formula:(5)SNRqn,ADC=6.02n+10lg3−10lgPAR.In the formulaPAR=maxst/Pavg20≤t≤T, it is related to the encoding format. For the WiMAX standard, PARWimax=3M−1/M+1.


### 2.3. Fiber Link

For fiber link, thermal noise is one of the important factors affecting the output error code. For the error rate of optical links, formula (6) can be used to calculate(6)BER=exp−Q2/22πQ,Q≥3.The noise powerPN=4Vmax222n−1/3×22nBER caused by the error code of the optical fiber link, where Vmax is the maximum voltage of the sampled signal. The power PDP=10lg1+DzBr2λ2/c is caused by the optical fiber dispersion, and the signal-to-noise ratio of the optical fiber link is shown in the following formula:(7)SNROL=10lg22n−11+4BER22n−1≈10lg22n−1.


### 2.4. DAC

DAC clock jitter noise is a Gaussian process with an average value of 0, and the resulting signal-to-noise ratio [15] is shown in the following formula:(8)SNRDAC=10lg2πσjn,DACfc−2sincfcfCLK−2,where fCLK is the sampling clock frequency and σji,DAC is the standard deviation of the root mean square jitter noise of the DAC.


### 2.5. VSA

The signal-to-noise ratio of each node of the system is quantitatively calculated in each subsystem model. The output signal-to-noise ratio after processing the bandwidth through the VSA can be expressed by the following formula:(9)SNRVSA=SNRlink+10lgfs2BVSA,where BVSA is the processing bandwidth of the VSA and SNRlink is the link signal-to-noise ratio under the condition of the sampling frequency of fs. When the above signal-to-noise ratios are all in linear units, as shown in the following formula,(10)1SNRlink=1SNRVSG+1SNRjn,ADC+1ANRqn,ADC+1SNROL+1SNRDAC.Introducing %EVMRMS and PAR, SNRVSA can be expressed by the following formula:(11)SNRVSA=−20lg%EVMRMS100−10lgPAR.The system error vector amplitude is obtained, as shown in the following formula:(12)%EVMRMS=100×10SNRVSA+10lgPAR/−20.Based on the construction of the intelligent optical fiber network, the microwave is regarded as the load carrier. First, the signal received by the central site is transmitted to the optical carrier through a certain modulation and demodulation, and the intelligent optical fiber is used for transmission to make the signal be detected by the detector at the terminal in the base station and received and transmitted further through portable antenna. The technology of intelligent optical fiber provides long-distance wireless access for radio frequency signals, as shown in Figure2. For microwave signals that have been modulated and demodulated, the intelligent microwave system is a carrier, a carrier of microwave, and can realize different carrier frequency adjustment. Because each network intelligence is concentrated in the central station, the transmission ratio control of each independent area signal can be realized through each central station, which not only simplifies the construction of the base station but also reduces the power consumption and cost of the entire system and facilitates the system upgrading and maintenance.Figure 2
Basic concept of ROF technology.


### 2.6. Typical WOBAN Network Composition

For the traditional WOBAN network, its characteristic is a tree-like structure. Its core is to use the central site to connect with the routing. The subrouters are used by multiterminal through I-fiber transmission signal to distribute the signals to each back end. The end is composed of corresponding routes to form a network to achieve acquisition, transmission, and response of data.In turn, any user can use the gateway to reach the back end and realize the spread. Through the use of multipoint control protocol, data transmission is realized, and the corresponding data are discarded to realize efficient and rapid response.


### 2.7. Reconfigurable Optical Wireless Network Structure

The optical wireless network part is another reconfigurable wireless network that is different from the above typical structure. It is a wireless mesh composed of multiple routes and multiple gateways. It is calculated based on the real-time status. Compared with the above typical structure, its structure can realize grid-based efficient management, make more effective use of optical fiber resources, and achieve stronger self-upgrading and maintenance capabilities.


## 2.1. VSG

The system sampling frequency/s depends on the sum of the maximum and minimum frequencies of the RF signalxi,tj=xminj+rand0,1∗xmaxj−xminj and ⇒. The conditions for no aliasing during the sampling process are as follows: vi,tj, where xi,tj, and the function ui,tj represents the largest integer not greater than x. When the symbol rate is xi,tj,vi,tj, the complex amplitude of the QAM signal can be obtained by the following formula:(1)st=Re∑ibt−iTAiejφiAejωcx.Among them,⇒, fui,t<fxi,t, xi,t⟵ui,t. fxi,t<fΔ, and Δ⟵xi,t are the amplitude and phase of the i-th character, respectively, b(t) is the signal pulse of unit amplitude, A is the amplitude of the RF carrier, T is the character duration, xi,t⟵xi,t is the angular frequency of the carrier. The frequency response of the pulse shaping filter can be obtained by the following formula:(2)Gf=1,f<fN1−α,12+12sinπ2fNfN−fα,fN1−α≤f≤fN1+α,0,f>fN1+α.In the formula,fN=1/2T WiMAX standard RF carrier frequency fc = 2.475 GHz, the bandwidth is 20 MHz, and the guard band bandwidth on both sides is 15 MHz each, so the total bandwidth of the RF carrier is 50 MHz. nz (3): the value range of nz is 1∼50. In this paper, nz=40, the sampling frequency is fs = 125MS/s. The band-pass signal is sampled out of band, and noise will enter the Nyquist area. The description of the band-pass signal noise is based on the assumption that both VSG in-band and out-of-band noise come from thermal noise. Thermal noise is a Gaussian process with a mean value of 0. The noise power PN=nzfsN0, where N0=kT/2, the VSG output signal-to-noise ratio can be calculated by the following formula:(3)SNRVSG=10lgPSPN=10lgPSnzfsN0.


## 2.2. ADC

Aperture and clock jitter will reduce the signal-to-noise ratio of the ADC. The jitter noise is approximately a Gaussian process with a mean value of 0. Assuming the input signalst=s0sin2πfct, the signal change rate ds/dt=2πfcs0cos2πfct, amplitude value is divided by 2 to get the root mean square value of ds/dt: ds/dtrms=2πfcs0/2/42. Let Δsrms be the root mean square noise, Δt is the standard deviation σjn,ADC of the root mean square jitter, and substituting it into the above formula to obtain Δsrms/σjn,ADC=2πfcs0/2, so that the root mean square noise obtained by the ADC is Δsrms=2πfcs0σjn,ADC/2. The root mean square value of the full-scale input sine wave is s0/2. Therefore, the ratio of the rms signal to the rms noise is calculated to obtain the signal-to-noise ratio between ADC noise and signal [13], as shown in the following formula:(4)SNRjn,ADC=−20lgΔsrmss0/2=−20lg2πfcσjn,ADC.Different from jitter noise, there is still quantization noise in the binary digital output of ADC, and it is related to the influence on the signal-to-noise ratio and carrier factor [14]. The specific calculation is shown in the following formula:(5)SNRqn,ADC=6.02n+10lg3−10lgPAR.In the formulaPAR=maxst/Pavg20≤t≤T, it is related to the encoding format. For the WiMAX standard, PARWimax=3M−1/M+1.


## 2.3. Fiber Link

For fiber link, thermal noise is one of the important factors affecting the output error code. For the error rate of optical links, formula (6) can be used to calculate(6)BER=exp−Q2/22πQ,Q≥3.The noise powerPN=4Vmax222n−1/3×22nBER caused by the error code of the optical fiber link, where Vmax is the maximum voltage of the sampled signal. The power PDP=10lg1+DzBr2λ2/c is caused by the optical fiber dispersion, and the signal-to-noise ratio of the optical fiber link is shown in the following formula:(7)SNROL=10lg22n−11+4BER22n−1≈10lg22n−1.


## 2.4. DAC

DAC clock jitter noise is a Gaussian process with an average value of 0, and the resulting signal-to-noise ratio [15] is shown in the following formula:(8)SNRDAC=10lg2πσjn,DACfc−2sincfcfCLK−2,where fCLK is the sampling clock frequency and σji,DAC is the standard deviation of the root mean square jitter noise of the DAC.


## 2.5. VSA

The signal-to-noise ratio of each node of the system is quantitatively calculated in each subsystem model. The output signal-to-noise ratio after processing the bandwidth through the VSA can be expressed by the following formula:(9)SNRVSA=SNRlink+10lgfs2BVSA,where BVSA is the processing bandwidth of the VSA and SNRlink is the link signal-to-noise ratio under the condition of the sampling frequency of fs. When the above signal-to-noise ratios are all in linear units, as shown in the following formula,(10)1SNRlink=1SNRVSG+1SNRjn,ADC+1ANRqn,ADC+1SNROL+1SNRDAC.Introducing %EVMRMS and PAR, SNRVSA can be expressed by the following formula:(11)SNRVSA=−20lg%EVMRMS100−10lgPAR.The system error vector amplitude is obtained, as shown in the following formula:(12)%EVMRMS=100×10SNRVSA+10lgPAR/−20.Based on the construction of the intelligent optical fiber network, the microwave is regarded as the load carrier. First, the signal received by the central site is transmitted to the optical carrier through a certain modulation and demodulation, and the intelligent optical fiber is used for transmission to make the signal be detected by the detector at the terminal in the base station and received and transmitted further through portable antenna. The technology of intelligent optical fiber provides long-distance wireless access for radio frequency signals, as shown in Figure2. For microwave signals that have been modulated and demodulated, the intelligent microwave system is a carrier, a carrier of microwave, and can realize different carrier frequency adjustment. Because each network intelligence is concentrated in the central station, the transmission ratio control of each independent area signal can be realized through each central station, which not only simplifies the construction of the base station but also reduces the power consumption and cost of the entire system and facilitates the system upgrading and maintenance.Figure 2
Basic concept of ROF technology.


## 2.6. Typical WOBAN Network Composition

For the traditional WOBAN network, its characteristic is a tree-like structure. Its core is to use the central site to connect with the routing. The subrouters are used by multiterminal through I-fiber transmission signal to distribute the signals to each back end. The end is composed of corresponding routes to form a network to achieve acquisition, transmission, and response of data.In turn, any user can use the gateway to reach the back end and realize the spread. Through the use of multipoint control protocol, data transmission is realized, and the corresponding data are discarded to realize efficient and rapid response.


## 2.7. Reconfigurable Optical Wireless Network Structure

The optical wireless network part is another reconfigurable wireless network that is different from the above typical structure. It is a wireless mesh composed of multiple routes and multiple gateways. It is calculated based on the real-time status. Compared with the above typical structure, its structure can realize grid-based efficient management, make more effective use of optical fiber resources, and achieve stronger self-upgrading and maintenance capabilities.


## 3. Differential Evolution Algorithm

For the differential evolution algorithm (Algorithm1), its characteristic is a global optimization algorithm, which uses search to perform a global search and achieves the optimal solution through crossover, compilation, and selection. The specific calculation process is as follows.Algorithm 1.
Input: population:M; crossed factor: D; number of iterations Tt ⟵ 1fori∼1 to M doforj = 1 to D doxi,tj=xminj+rand0,1∗xmaxj−xminj;endendwhile(|f(Δ)| > ε) or (t ≤ T)dofori = 1 to M do⇒ (Mutation and Crossover)forj = 1 to D dovi,tj =Mutation(xi,tj);ui,tj =Crossoverxi,tj,vi,tj;end⇒ (Selection)if theniffui,t<fxi,t thenxi,t⟵ui,t;iffxi,t<fΔ thenΔ⟵xi,t;endelsexi,t⟵xi,t;endendt = t + 1endreturn the best Δ


## 4. Key Technology Analysis

### 4.1. Optical Distributed Antenna Technology

For the optical distributed antenna system, it uses smart optical fiber to realize the link between the antenna and the node of the center of gravity. The antenna only needs to complete the conversion between the optical signal and the electrical signal and does not need to care about modulation and demodulation, but with the increase of the amount of data, the antenna system needs to complete the photoelectric signal conversion more efficiently, which puts forward higher requirements on the antenna technology. Therefore, in terms of research, through the realization of distributed antenna simulation, the optical signal is distributed to different terminal antennas and is processed in a distributed manner at the same time to achieve high efficiency of the effectiveness and time and to meet the centralized management of the system [14, 15].


### 4.2. Cognitive Radio Technology

For radio technology, it is an improvement technology for the frequency spectrum. For example, the corresponding parameters can be adjusted adaptively to face the complex transmission environment to achieve the double balance of transmission distance and transmission efficiency. On the other hand, it can access the required spectrum autonomously and dynamically according to the results of related perception. For different users and different needs, distributed radio technology is needed to realize the management and adaptive adjustment of optical signals.


### 4.3. Low-Power Green Smart Optical Fiber Technology

The focus concerned by low-power smart optical fiber technology is to use low-power and low-energy technologies, for reducing network energy consumption, which is of great significance to enterprises, governments, and individuals. Therefore, “green” interconnection not only reduces cost but also reduces energy consumption. The deployment of a large number of terminal devices consumes bandwidth and coverage while also bringing a large amount of consumption. Therefore, the intelligent optical fiber technology required for realization of low power consumption requires optimizing and improving the corresponding routing algorithm. When the power is minimized, the bandwidth can be balanced and the equipment can be accessed in an orderly manner.


## 4.1. Optical Distributed Antenna Technology

For the optical distributed antenna system, it uses smart optical fiber to realize the link between the antenna and the node of the center of gravity. The antenna only needs to complete the conversion between the optical signal and the electrical signal and does not need to care about modulation and demodulation, but with the increase of the amount of data, the antenna system needs to complete the photoelectric signal conversion more efficiently, which puts forward higher requirements on the antenna technology. Therefore, in terms of research, through the realization of distributed antenna simulation, the optical signal is distributed to different terminal antennas and is processed in a distributed manner at the same time to achieve high efficiency of the effectiveness and time and to meet the centralized management of the system [14, 15].


## 4.2. Cognitive Radio Technology

For radio technology, it is an improvement technology for the frequency spectrum. For example, the corresponding parameters can be adjusted adaptively to face the complex transmission environment to achieve the double balance of transmission distance and transmission efficiency. On the other hand, it can access the required spectrum autonomously and dynamically according to the results of related perception. For different users and different needs, distributed radio technology is needed to realize the management and adaptive adjustment of optical signals.


## 4.3. Low-Power Green Smart Optical Fiber Technology

The focus concerned by low-power smart optical fiber technology is to use low-power and low-energy technologies, for reducing network energy consumption, which is of great significance to enterprises, governments, and individuals. Therefore, “green” interconnection not only reduces cost but also reduces energy consumption. The deployment of a large number of terminal devices consumes bandwidth and coverage while also bringing a large amount of consumption. Therefore, the intelligent optical fiber technology required for realization of low power consumption requires optimizing and improving the corresponding routing algorithm. When the power is minimized, the bandwidth can be balanced and the equipment can be accessed in an orderly manner.


## 5. ROF-Based Automatic Transmission Characteristics of Radio Frequency

### 5.1. Single-Sideband Transmission Characteristics

For wireless radio frequency automation, a smart optical fiber system for unilateral transmission is chosen in this paper. On the one hand, this can improve the signal attenuation caused by fiber dispersion and increase the distance for effective transmission. On the other hand, compared with the bilateral transmission method, the bandwidth occupied by it is smaller and the cost is lower. According to the principle of unilateral transmission, a corresponding transmission system is constructed in this paper, and corresponding research is conducted on the characteristics of transmission, as shown in Figure3.Figure 3
Long optical fiber microwave optical fiber transmission system.For the corresponding signal generated from radio frequency, the light carrier is realized in the form of light loading through modulator-demodulator. Through long-distance transmission, one part of signal is filtered, while the other part needs to be detected through detector for the transmission condition.The result of the optical single-sideband signal generated after the filter is shown in Figure4. Based on the result, the spectrum output contains the signal of the optical carrier and the sideband signal, and the remaining signals have been filtered out. On this basis, the corresponding signal modulation is put on microblog to carry on the quality performance test to the received signal; the error vector value is about 9%; the signal-to-noise ratio is about 20 dB.Figure 4
Optical single-sideband signal generated through the filter.


### 5.2. Double-Sideband Carrier Suppressed Transmission Characteristics

The frequency conversion of the photoelectric transmission signal is realized to reduce the adverse effects of the dispersion of the optical fiber in this paper. The specific block diagram is shown in Figure5:Figure 5
System functional block diagram based on double-sideband carrier suppression.For the overall system, when the frequency conversion of the carrier signal is realized, the change and conversion of the photoelectric signal are also realized, and the received signal-to-noise ratio is about 24.8%, which can meet the requirements of wireless communication for the quality of related signals.(1)
According to the above algorithm, the quantitative estimates can be performed effectively for the relationship between the resolution and the signal-to-noise ratio. From the calculation results, when the resolution is less than 6 bits, the quantified signal-to-noise ratio plays a dominant role. On the contrary, when the resolution is greater than 7 bits, the result of link signal-to-noise ratio is equal to the resolution signal-to-noise ratio. Therefore, 8 bits is the corresponding threshold result, and the signal-to-noise ratio result is about 39 dB.(2)
We calculated the specific relationship between the response link and the bit error rate. The calculated result is as shown in Figure6. From the results, there is negative correlation between the bit error rate and the optical link. Therefore, when the number of optical links increases, the response bit error rate is effectively reduced.(3)
The calculation result between the system error vector and the resolution is shown in Figure7. From the results, it can be seen that when the resolution is less than 7 bits, the system error vector is negatively correlated with the ADC. When the resolution reaches 8 bits, the system error vector and ADC are in an undesirable state, and the value is stable, about 0.7%. Therefore, 8 bits can be regarded as a stable resolution threshold.(4)
As an important indicator, the signal-to-noise ratio of the system link is determined by the resolution of the ADC. Therefore, in order to study more appropriately, the system error is calculated as the relationship between the important influencing factor and the signal-to-noise ratio. The specific results are shown in Figure8. From the results, it can be seen that when the signal-to-noise ratio result is less than 35 dB, the system’s error vector value is negatively correlated with the signal-to-noise ratio; on the contrary, when the signal-to-noise ratio result is greater than 35 dB, the error vector value of the system has no obvious relationship with the signal-to-noise ratio.Figure 6
The relationship between BER andQ.Figure 7
The relationship between %EVMRMS andn.Figure 8
The relationship between %EVMRMS and SNRlink.In combination with the above results, it can be seen that the result of the differential evolution algorithm can make the ADC resolution reach 8 bits, which effectively realizes the optimization of the system signal-to-noise ratio. When the signal-to-noise ratio of the system chain is determined by the system error and the calculated result reaches 36 dB, the optimal error value is about 0.7%, which proves the superiority of the differential evolution algorithm and can effectively support the wireless radio frequency automation of the intelligent optical fiber transmission system.


## 5.1. Single-Sideband Transmission Characteristics

For wireless radio frequency automation, a smart optical fiber system for unilateral transmission is chosen in this paper. On the one hand, this can improve the signal attenuation caused by fiber dispersion and increase the distance for effective transmission. On the other hand, compared with the bilateral transmission method, the bandwidth occupied by it is smaller and the cost is lower. According to the principle of unilateral transmission, a corresponding transmission system is constructed in this paper, and corresponding research is conducted on the characteristics of transmission, as shown in Figure3.Figure 3
Long optical fiber microwave optical fiber transmission system.For the corresponding signal generated from radio frequency, the light carrier is realized in the form of light loading through modulator-demodulator. Through long-distance transmission, one part of signal is filtered, while the other part needs to be detected through detector for the transmission condition.The result of the optical single-sideband signal generated after the filter is shown in Figure4. Based on the result, the spectrum output contains the signal of the optical carrier and the sideband signal, and the remaining signals have been filtered out. On this basis, the corresponding signal modulation is put on microblog to carry on the quality performance test to the received signal; the error vector value is about 9%; the signal-to-noise ratio is about 20 dB.Figure 4
Optical single-sideband signal generated through the filter.


## 5.2. Double-Sideband Carrier Suppressed Transmission Characteristics

The frequency conversion of the photoelectric transmission signal is realized to reduce the adverse effects of the dispersion of the optical fiber in this paper. The specific block diagram is shown in Figure5:Figure 5
System functional block diagram based on double-sideband carrier suppression.For the overall system, when the frequency conversion of the carrier signal is realized, the change and conversion of the photoelectric signal are also realized, and the received signal-to-noise ratio is about 24.8%, which can meet the requirements of wireless communication for the quality of related signals.(1)
According to the above algorithm, the quantitative estimates can be performed effectively for the relationship between the resolution and the signal-to-noise ratio. From the calculation results, when the resolution is less than 6 bits, the quantified signal-to-noise ratio plays a dominant role. On the contrary, when the resolution is greater than 7 bits, the result of link signal-to-noise ratio is equal to the resolution signal-to-noise ratio. Therefore, 8 bits is the corresponding threshold result, and the signal-to-noise ratio result is about 39 dB.(2)
We calculated the specific relationship between the response link and the bit error rate. The calculated result is as shown in Figure6. From the results, there is negative correlation between the bit error rate and the optical link. Therefore, when the number of optical links increases, the response bit error rate is effectively reduced.(3)
The calculation result between the system error vector and the resolution is shown in Figure7. From the results, it can be seen that when the resolution is less than 7 bits, the system error vector is negatively correlated with the ADC. When the resolution reaches 8 bits, the system error vector and ADC are in an undesirable state, and the value is stable, about 0.7%. Therefore, 8 bits can be regarded as a stable resolution threshold.(4)
As an important indicator, the signal-to-noise ratio of the system link is determined by the resolution of the ADC. Therefore, in order to study more appropriately, the system error is calculated as the relationship between the important influencing factor and the signal-to-noise ratio. The specific results are shown in Figure8. From the results, it can be seen that when the signal-to-noise ratio result is less than 35 dB, the system’s error vector value is negatively correlated with the signal-to-noise ratio; on the contrary, when the signal-to-noise ratio result is greater than 35 dB, the error vector value of the system has no obvious relationship with the signal-to-noise ratio.Figure 6
The relationship between BER andQ.Figure 7
The relationship between %EVMRMS andn.Figure 8
The relationship between %EVMRMS and SNRlink.In combination with the above results, it can be seen that the result of the differential evolution algorithm can make the ADC resolution reach 8 bits, which effectively realizes the optimization of the system signal-to-noise ratio. When the signal-to-noise ratio of the system chain is determined by the system error and the calculated result reaches 36 dB, the optimal error value is about 0.7%, which proves the superiority of the differential evolution algorithm and can effectively support the wireless radio frequency automation of the intelligent optical fiber transmission system.


## 6. Conclusions

The development of smart optical fiber has given birth to more wireless radio frequency automation technology developments. In view of performance evaluation and other requirements, differential evolution algorithm is introduced in this paper for fusion construction through the integration of optical and wireless networks, and the idea of bilateral transmission is proposed, and the quality requirement of demodulated signal is met through photoelectric signal conversion. On this basis, the corresponding intelligent optical fiber system is introduced, which has the characteristics of high efficiency and long transmission distance and realizes further performance optimization and enhancement of wireless communication.



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