Yuanjian Wan, Xudong Liu, Guangze Wu, Min Yang, Guofeng Yan, Yu Zhang, Jian Wang. Efficient stochastic parallel gradient descent training for on-chip optical processor[J]. Opto-Electronic Advances, 2024, 7(4): 230182

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- Opto-Electronic Advances
- Vol. 7, Issue 4, 230182 (2024)

Fig. 1. (a ) Conceptual diagram of the on-chip optical processor for optical switching and channel descrambling in MDM communication systems. (b ) Schematic configuration of the integrated reconfigurable optical processor. θ and ϕ mean the phase shift of the phase shifters. MDM: mode-division multiplexing; MUX: multiplexer; DEMUX: demultiplexer.

Fig. 2. Flow chart of Stochastic Parallel Gradient Descent (SPGD) algorithm.

Fig. 3. Training results in electronic computer for optical switching, optical channel descrambling, and optical channel descrambling and switching. (a ) Emulated light power distributions and (b ) normalized light intensity distributions after training when the switching state is I1−O2, I2−O1, I3−O5, I4−O6, I5−O3, I6−O4. (d , e ) Normalized light intensity distributions (d) before and (e) after training when randomly generating a set of phases in the part (1) of our chip to emulate crosstalk. (g , h ) Normalized light intensity distributions (g) before and (h) after training with crosstalk when the switching state is: I1−O5, I2−O3, I3−O2, I4−O4, I5−O1, I6−O6. (c , f, i ) The evaluation function changing with iteration rounds.

Fig. 4. (a ) Schematic of experimental configuration. (b ) Microscopy image of optical processor. VSA: voltage source array; PD: photodetector array.

Fig. 5. Online training results for optical switching at a wavelength of 1550 nm. (a ) The evaluation function changing with iteration rounds when the switching state is I1−O3, I2−O1, I3−O4, I4−O6, I5−O2, I6−O5. The insets figures show the light power distributions when the round of iteration equals 50, 300, and 600, respectively. (b ) The measured light power distributions after training. (c ) The normalized light intensity distributions of measured results. (d , e ) The measured light power distributions and normalized light intensity distributions when the switching state is I1−O3, I2−O6, I3−O4, I4−O2, I5−O1, I6−O5.

Fig. 6. Online training results for optical channel descrambling at a wavelength of 1550 nm. (a ) The evaluation function changing with iteration rounds. The insets show the light power distributions when the round of iteration equals 1, 300, and 600, respectively. (b ) The light power distributions before training. (c ) The light power distributions after training. (d , e ) The results of training when generating another matrix .

Fig. 7. Online training results for optical channel descrambling and switching at a wavelength of 1550 nm. (a ) The evaluation function changing with iteration rounds when the switching state is I1−O4, I2−O1, I3−O5, I4−O6, I5−O3, I6−O2. The insets show the light power distributions when the round of iteration equals 1, 100, and 400, respectively. (b ) The light power distributions before training. (c ) The light power distributions after training. (d , e ) The results of training when generating another matrix and the switching state is I1−O5, I2−O3, I3−O1, I4−O6, I5−O2, I6−O4.

Fig. 8. Experimental setup and measured results for optical channel descrambling. (a ) Experimental setup for the 6×6 optical descrambling systems. (b ) The measured BER performance for back-to-back, optimization without crosstalk, before optimization with crosstalk, and after optimization with crosstalk systems. (c ) The measured constellation chart at the back-to-back. (d ) The measured constellation chart without crosstalk. (e ) The measured constellation chart before optimization with crosstalk. (f ) The measured constellation chart after optimization with crosstalk. PC: polarization controller; AWG: arbitrary waveform generator; EDFA: erbium-doped fiber amplifier; VOA: variable optical attenuator; OSC: oscilloscope; DSP: digital signal processing.
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Table 1. Performance of different algorithms.

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