In this Letter, we propose a monitoring and control system (MCS) for operating tunable optical delay lines (TODLs), regardless of their operation principle and implementation technology. The monitoring system resorts to two out-of-band pilot tones added to the input optical signal. The amplitude and phase difference between tones are retrieved to the control system, which calculates and applies the TODL control signals. The MCS was validated using a Mach–Zehnder delay interferometer-based TODL, implemented in three different silicon photonic integrated circuits (PICs). The three PICs resort to different kinds of phase shifters based on thermo-optic, carrier-injection, and carrier-depletion effects. The proposed MCS enabled tuning the delay within the entire range of the TODL in all tested PICs. The scalability of the MCS for large-scale photonic beamformers is discussed.

中文翻译：

---

可调光延迟线的可重构监控系统

在本函中，我们提出了一种用于监视可调谐光延迟线（TODL）的监视和控制系统（MCS），而不论其工作原理和实现技术如何。监视系统采用添加到输入光信号中的两个带外导频音。音调之间的幅度和相位差被检索到控制系统，该系统计算并应用TODL控制信号。MCS使用基于Mach-Zehnder延迟干涉仪的TODL进行了验证，该TODL在三种不同的硅光子集成电路（PIC）中实现。这三个PIC基于热光，载流子注入和载流子耗尽效应，采用了不同种类的移相器。拟议的MCS支持在所有测试的PIC中在TODL的整个范围内调整延迟。