Abstract
Integrated optical true time delay lines attract lots of attention for optically controlled mm-wave beam steering due to its low-loss/broadband performance and stable/compact system architecture. However, for remotely-controlled networks, the techniques that require local-site actively-tuned elements would make the network control more complicated. A passive design using wavelength-tuning is regarded as a promising candidate. In this paper, an integrated wavelength-tuned optical mm-wave beamformer with doubled delay resolution is proposed and demonstrated in a generic InP platform. A bidirectional looped-back arrayed waveguide grating (AWG) module acts as the stepwise tunable delay unit. By introducing an extra AWG router for delay mode (positive/negative) selection and a bidirectional optical interface, a pure λ-tuned, resolution-doubled optical delay network is realized without using any active component (e.g. heaters, current injection) at the local site. This photonic passive design is more beneficial to the remotely-controlled mm-wave beam steering system. Furthermore, the AWG router potentially allows multi-port wavelength switching to support the scaling-up of the network. The fabrication-caused delay error of <1.1 ps is experimentally verified on-chip. A further proof-of-concept 38-GHz fiber-wireless beam steering system with a 186° angular steering is experimentally demonstrated using QAM-4 modulation. Accurate mm-wave phase shifts originated from the proposed optical beamformer are obtained, which proves the effectiveness of the tunable integrated beamformer.
Original language | English |
---|---|
Article number | 8985297 |
Pages (from-to) | 2353-2359 |
Number of pages | 7 |
Journal | Journal of Lightwave Technology |
Volume | 38 |
Issue number | 8 |
DOIs | |
Publication status | Published - 15 Apr 2020 |
Keywords
- Indoor fiber-wireless communications
- integrated photonics
- looped-back AWG
- optical mm-wave beamformer
- wavelength-tuned