LI-FI based image transmission using ESP32

Dears, i'm working on a LiFi image transmission project using ESP32 microcontrollers. I then use 2 microcontrollers, one as transmitter through laser and another as receiver through an LDR. So far, the Arduino codes and Python script i've used for the transmission aren't working so far.

PYTHON CODE TO CONVERT IMAGE TO STRING:

import base64
def image_to_base64(image_path):
 with open(image_path, "rb") as img_file:
 # Read the image file in binary mode
     img_data = img_file.read()
 # Encode the binary data as base64
 base64_data = base64.b64encode(img_data)
 # Decode bytes to string
 base64_string = base64_data.decode("utf-8")
 return base64_string
# Example usage
image_path = "blue.png" # Replace with your image file path
base64_string = image_to_base64(image_path)
print(base64_string) 

ARDUINO CODE TO TRANSFER IMAGE:

#define LED_PIN 22
// #define BUTTON_PIN A0
//const int LED_PIN = 2;
#define PERIOD 15
char *string ="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#";
int string_length;
void setup()
{
 pinMode(LED_PIN, OUTPUT);
  pinMode(3, INPUT);
  digitalWrite(3,LOW);
 string_length = strlen(string);
  delay(5000);
 if(digitalRead(3) == HIGH){
 for(int i = 0; i < string_length; i ++)
 {
 send_byte(string[i]);
 }
 delay(10);
 }
}
void loop()
{ 
}
void send_byte(char my_byte)
{
 digitalWrite(LED_PIN, LOW);
 delay(PERIOD);
 //transmission of bits
 for(int i = 0; i < 8; i++)
 {
 digitalWrite(LED_PIN, (my_byte&(0x01 << i))!=0 );
 delay(PERIOD);
 }
 digitalWrite(LED_PIN, HIGH);
 delay(PERIOD);
}

PYTHON CODE TO RECEIVE IMAGE:

import serial 
import base64 
from io import BytesIO 
from PIL import Image 
import time 
import binascii
from serial import Serial
long_string = "" 
fixed_base64_str = "" 
ser = serial.Serial('COM5', 9600, timeout=15) 
ser.reset_input_buffer()
#time.sleep(2) 
while True: 
     if ser.in_waiting > 0: 
         data = ser.read().decode('utf-8')  
         long_string += data 
         print(data, end="") 
         if " " in long_string: 
            break
ser.close() 
long_string = long_string[:-1] 
print(f"\n\n{long_string}\n\n")
# Decode the image from the fixed base64 string 
image_bytes = base64.b64decode(fixed_base64_str) 
image = Image.open(BytesIO(image_bytes)) 
image.show() 

Emission circuit

ARDUINO CODE TO RECEIVE:

#define LED_PIN 3 
#define LDR_PIN 34 
#define THRESHOLD 300
#define PERIOD 15 
bool previous_state,current_state; 
void setup() 
 {Serial.begin(9600); 
 pinMode(LED_PIN, OUTPUT);} 
void loop() 
 {current_state = get_ldr(); 
 if(!current_state && previous_state) 
 {print_byte(get_byte());} 
 previous_state = current_state;} 
bool get_ldr() 
 {int voltage = analogRead(LDR_PIN); 
 //Serial.println(voltage);
 return voltage > THRESHOLD ? true : false;} 
char get_byte() 
 {char ret = 0; 
 delay(PERIOD*1.5); 
 for(int i = 0; i < 8; i++){ 
 ret = ret | get_ldr() << i; 
 delay(PERIOD);} 
 return ret;} 
void print_byte(char my_byte) 
{char buff[2];
 sprintf(buff, "%c", my_byte);
 Serial.println(buff);}

RECEPTION CIRCUIT

When I run Python receiver code, I got this error:

Traceback (most recent call last):
  File "C:\Users\Yasmine\AppData\Local\Programs\Python\Python312\coderecep.py", line 15, in <module>
    data = ser.read().decode('utf-8')
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe3 in position 0: unexpected end of data

I tried to adjust the synchronisation threshold between 210 and 800, but it did not work.