# Adaptive Linearization for the Sub-Nyquist Photonic Receiver Based on Deep Learning  
[PERSON]  
1 State Key Laboratory of High Performance Computing, College of Computer Science and Technology,  
National University of Defense Technology, Changsha 410073, China 1, [PERSON]  
2 National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China,  
Beijing 100071, China 2, [PERSON]  
2 National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China,  
Beijing 100071, China 2, [PERSON]  
1 State Key Laboratory of High Performance Computing, College of Computer Science and Technology,  
National University of Defense Technology, Changsha 410073, China 1, [PERSON]  
2 National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China,  
Beijing 100071, China 2, [PERSON]  
2 National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China,  
Beijing 100071, China 2,  
[PERSON]  
2 National Innovation Institute of Defense Technology, Academy of Military Sciences PLA China,  
Beijing 100071, China 2, [PERSON]  
Changsha 410073, China 3 College of Advanced Interdisciplinary Studies, National University of Defense Technology,
sub-Nyquist photonic receivers [12]. Compared to the channelization system, the Sub-Nyquist photonic receivers employ a single low-speed ADC [13], which obviates redundant hardware setups, and saves power consumption [14; 15]. The architecture of sub-Nyquist photonic receivers [16] originates from the sampled (pulse-based) analog photonic link [17]. The sampled analog photonic link is applied in wideband radio frequency (RF) signal receivers with carrier frequencies of up to 40 GHz and a bandwidth of 20 MHz [18]. Nevertheless, the sinusoidal-like transfer response of the electro-optic modulator (EOM) inherently leads to nonlinear distortions [19; 20]. In addition, the low noise amplifiers (LNAs) for RF signals also induce unexpected nonlinear distortions and inevitable noise. Besides, the harmonic distortions (HD) and intermodulation distortions (IMD) are folded into the first Nyquist zone (NZ) of the sampled analog photonic link. The spurious harmonics of signals with large frequency intervals may produce new aliasing and intermodulation components. In addition, the sampled analog photonic link down-converts the thermal noise and shot noise from all Nyquist zones to the first Nyquist zone. These put immense pressure on the back-end signal processing and seriously deteriorate the working bandwidth, reconnaissance distance, signal-to-noise ratio (SNR), and signal bit error rate (BER). Hence, the intricate spurious distortions and noises of the sampled analog link place restrictions on its practical application in wideband receivers. There are considerable publications focusing on the linearization of the sampled analog photonic link with nonlinear distortions introduced by EOM. [PERSON] et al. achieved the suppression of third-order intermodulation distortions by 25 dB with an instantaneous bandwidth of 500 MHz [21]. [PERSON]. [PERSON] et al. applied pre-distortion linearization to improve the spur-free dynamic range (SFDR) of an externally modulated, long-haul analog fiber-optic link by 6 dB in the band range of 6-12 GHz, which may have brought about significant imperfections at the same time [22]. Besides, [PERSON] et al. proposed a digital processing compensation method that realized the suppression of the third-order intermodulation distortion (IMD3) by more than 20 dB [20]. [PERSON] et al. published digital post-compensation methods for a photonic sampling link that realized the suppression of the cross-modulation distortion (XMD) and IMD3 by 33 dB and 25 dB, respectively, which could perform poorly under large dispersion after long-distance transmission [23]. [PERSON] et al.