# Theory of AdaDelSPGD Algorithm in Fiber Laser-Phased Array Multiplex Communication Systems
## 3 Experiment  
To verify the effectiveness of the algorithm, experiments are carried out in a three-channel fiber laser-phased array multichannel communication system. Figure 4a shows the experimental set-up, and Figure 4b shows the actual experiment. The experimental device is shown in Figure 4. For the convenience of display, the distance between PD and BS is reduced, while the actual distance is about 19 m, and the actual distance between BS and OFC is approximately 20 m or 3 km. The schematic diagram and the experimental process have been described in Section 2. Now, I will introduce the equipment used in the experiment used in each subsystem of the experiment in detail.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**N** & **SPGD** & **AdaDelSPGD** & **Rate** \\ \hline
3 & 18 & 13 & 38.4\% \\
7 & 52 & 36 & 44.4\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: The numerical results of the convergence speed.  
Figure 4: Diagram of the experimental device of the three-channel fiber laser-phased array multiplex communication system. (**a**) Set-up of the experiment; (**b**) experimental images.  
In the laser emission subsystem, the seed source is a single-mode polarization-maintaining laser at 1064 nm, and the laser linewidth is less than 20 kHz. After passing through the inner part of the beam, the output power of the three laser channels is 1 mW.  
The communication modulation subsystem adopts the bit error rate analyzer and microwave amplifier as the communication modulation signal input, and the intensity modulator is the ixBlue company's 10 GHz intensity modulator.  
The phase modulator in the phase locking subsystem is an ixBlue phase modulator with a maximum modulation frequency of 150 MHz for a 1064 nm laser. The V-groove is custom made. The outer diameter of the optical fiber is 125 um, and the distance between the centers of the three optical fibers is 127 um after passing through the V-shaped groove. Therefore, the three optical fibers are closely arranged in the V-shaped groove. A spectroscopic transmits 90% of the light and reflects 10%. The detector is indium gallium as photodiode detector, with the maximum detection power of 10 mW. Since the three channels have a total of 3 mW, no attenuation film is used. The controller adopts DSP development board. The DSP algorithm control board algorithm processing core device is TMS320F2812 chip. The main frequency of the chip is 150 MHZ. The A/D sampling module of the data acquisition part is AD976 chip, and the output D/A module uses two AD8544 chips.  
In the communication receiving subsystem, there are four collimators altogether. Under laboratory conditions, only one collimator is coupled into the optical fiber. In the long-distance experiment, the compression divergence angle of the optical system was added to the emitter, but the diameter of the synthetic spot at 3 km was still 1 m. Therefore, four collimators are used to receive at the same time. Finally, when calculating the bit error rate, the four-bit error rates are averaged to increase the accuracy. The fiber amplifier model is YDFA-PA-MSA, and the detector is the THORLARS 'RXM25 AF detector, with a frequency ranging from 500 kHz to 25 GHz. The oscilloscope model is Lecroy SDA813 Zi. The bandwidth is 13 GHz. The eye chart and bit error rate were observed via oscilloscope.