Mixed-signal frequency control loop for tunable laser

Abstract

A Lidar system includes a tunable laser (TL) configured to generate an output light signal (L) and a photodiode array for receiving light (R) from the tunable laser reflected from a target object (O).The tunable laser includes a feedback loop including a Mach-Zender interferometer, MZI, receiving the output light signal from the tunable laser, in which the MZI includes two optical paths receivingthe output light signal. A phase shifter is provided in one optical path that is operable to produce a pre-determined shift in the phase angle of the light signal passing through the one optical pathrelative to the phase angle of the light signal passing through the other optical path. A photodiode configured to detect the interference signal generated by the MZI is operable to generate a photodiode current (iPD) in response thereto. Circuitry converts the photodiode current to a control signal for controlling the tunable laser.

Description

[0001] Cross References to Related Applications [0002] This application is an invention application claiming priority to co-pending Provisional Application No. 62 / 608,667, filed December 21, 2017, the entire disclosure of which is incorporated herein by reference. Background technique [0003] Advanced three-dimensional (3D) cameras have been developed that can scan a scene or object and develop a very accurate 3D model or image. Some 3D cameras use lidar (light imaging, detection, and ranging), which uses pulsed laser light to measure range or distance. like figure 1 As shown, a typical lidar system includes: a scanning transmitter that emits laser light (TX light); and a receiver for receiving reflected light (RX light) that includes a photoreceptor such as a photodiode. The transmitter includes: a laser modulation circuit and a beam steering circuit to control the operation of the laser. Signals from the photoreceptors are fed to processing circuitry that converts the ...

AI Technical Summary

Problems solved by technology

[0013] Although Figure 5a The PLL controller shown provides an efficient technique for some systems, but it still has certain limitations in many practical situations

In particular, when the differential time delay between two MZI waveguide branches ( τ MZI ) cannot be long enough, such as when the controller is integrated onto a photonic chip with a small functional area, problems can arise

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