Comprehensive vector analysis for electro-optical, opto-electronic, and optical devices.

High-performance electro-optical (E-O), opto-electronic (O-E), and optical (O-O) devices are widely used in optical communications, microwave photonics, fiber sensors, and so on. Measurement of the amplitude and phase responses are essential for the development and fabrication of these devices. However, the previous methods can hardly characterize the E-O, O-E, and O-O devices with arbitrary responses. Here we propose a comprehensive vector analyzer based on optical asymmetrical double-sideband (ADSB) modulation to overcome this difficulty. The ADSB solves the problem of frequency aliasing and can extract information from both the +1st- and -1st-order sidebands. Thus, most devices in photonic applications, including phase modulators, can be characterized. In the experiment, a commercial photodetector, a phase modulator, and a sampled FBG are used as the O-E, E-O, and O-O devices under test, respectively. A frequency resolution of 2 MHz, an electrical sweeping range of 40 GHz, and an optical sweeping range of 80 GHz are achieved.

Ultrafast and ultrahigh-resolution optical vector analysis using linearly frequency-modulated waveform and dechirp processing.

We propose and experimentally demonstrate an ultrafast and ultrahigh-resolution optical vector analyzer (OVA) using linearly frequency-modulated (LFM) waveform and dechirp processing. An optical LFM signal, achieved by modulating an electrical LFM signal on an optical carrier via carrier-suppressed optical single-sideband (OSSB) modulation, is separated into two portions. One portion (denoted as the reference signal) directly goes through the reference path, and the other (denoted as the probe signal) undergoes magnitude and phase changes by an optical device under test (DUT) in the measurement path. After balanced photodetection, the reference signal and the probe signal are mixed to perform a dechirp operation. A relatively low-frequency electrical signal is generated, which can be sampled by a low-speed analog-to-digital converter. As a result, the frequency responses of the DUT can be extracted at a high speed by post digital signal processing. Thanks to the large chirp rate of the electrical LFM signal and the dechirp processing, the proposed LFM-based OVA enables ultrafast measurement speed and ultrahigh frequency resolution. We perform an experiment in which a narrowband tunable optical filter is characterized. The measurement speed reaches 1 ns/point, and the frequency resolution is 1.6 MHz.

Ultrahigh-resolution and wideband optical vector analysis for arbitrary responses.

An ultrahigh-resolution and wideband optical vector analyzer (OVA) with the simplest architecture, to the best of our knowledge, is proposed and demonstrated based on chirped optical double-sideband (ODSB) modulation in a single-drive Mach-Zehnder modulator (MZM). To distinguish the magnitude and phase information carried by the two sidebands in the ODSB signal, a two-step measurement, in which biasing, respectively, the MZM at two different points is applied. Because no optical filtering is required in the scheme, the optical carrier can be located at any wavelength that is suitable for accurate measurement, e.g., close to the notch of a notch response or within the passband of a bandpass response, so the proposed OVA has the capability to measure an arbitrary response. An experiment is carried out, which achieves the magnitude and phase responses of a programmable optical processor with bandpass, notch, or falling-edge responses. The measurement bandwidth is 134 GHz, and the measurement resolution is 1.12 MHz.