Abstract

We demonstrate a broadband and continuously tunable 1×4 optical beamforming network (OBFN), based on the hybrid integration of indium phosphide (InP) components in the silicon nitride (Si₃N₄) platform. The photonic integrated circuit (PIC) comprises a hybrid InP-Si₃N₄ external cavity laser, a pair of InP phase modulators, a Si₃N₄ optical single-sideband full carrier (SSBFC) filter followed by four tunable optical true time delay lines (OTTDLs), and four InP photodetectors. Each OTTDL consists of eight cascaded thermo-optical micro-ring resonators (MRRs) that impose tunable true time delay on the propagating optical signals. The OBFN-PIC is designed to facilitate the steering of a microwave signal with carrier frequency up to 40 GHz over a continuous set of beam angles. We evaluate the performance of the OBFN-PIC to handle and process microwave signals, measuring the link gain, the noise figure (NF), and the spurious-free dynamic range (SFDR) parameters. Moreover, we assess its beamforming capabilities assuming that the OBFN-PIC is part of a wireless system operating in the downlink direction and feeds a multi-element antenna array. Using microwave signals at 5 and 10 GHz with quadrature amplitude modulation (QAM) formats at 500 Mbaud, we evaluate the performance of the OBFN-PIC under various configurations. We show that error-free performance can be achieved at both operating frequencies and for all the investigated beam angles ranging from 45° to 135°, thus validating its potential for high-quality beamforming performance.

Continuously tunable silicon optical true-time delay lines with a large delay tuning range and a low delay fluctuation

Yuanbin Liu, Liangjun Lu, Ziheng Ni, Jianping Chen, Linjie Zhou, and Andrew W. Poon
Opt. Express 32(5) 7848-7864 (2024)

Silicon integrated microwave photonic beamformer

Chen Zhu, Liangjun Lu, Wensheng Shan, Weihan Xu, Gangqiang Zhou, Linjie Zhou, and Jianping Chen
Optica 7(9) 1162-1170 (2020)

Optical true time delay unit for multi-beamforming

Xingwei Ye, Fangzheng Zhang, and Shilong Pan
Opt. Express 23(8) 10002-10008 (2015)

Integrated waveguide true time delay beamforming system based on an SOI platform for 28 GHz millimeter-wave communication

Yun Han, Shuangjin Shi, Rongting Jin, YunXiang Wang, and Qi Qiu
Appl. Opt. 59(26) 7770-7778 (2020)

On-chip optical true time delay lines based on subwavelength grating waveguides

Yue Wang, Hao Sun, Mostafa Khalil, Wei Dong, Ivana Gasulla, José Capmany, and Lawrence R. Chen
Opt. Lett. 46(6) 1405-1408 (2021)