Jianguo Shen

A Photonic RF Phase Shifter Based on a Dual-Parallel Mach–Zehnder Modulator and an Optical Filter

A photonic RF phase shifter using a dual parallel Mach–Zehnder modulator (DPMZM) and a tunable optical band-pass filter is demonstrated. The dependences of the linearity and power stability of the proposed RF phase shifter on the performance of the DPMZM and the optical filter are theoretically analyzed and numerically simulated. In the experiment, a continuously tunable range of more than 450° phase shift and a small power variation of less than 1.6 dB for a wideband RF range (8–12 GHz) are achieved by simply tuning the bias voltage of the DPMZM. The experimental results agree well with the theoretical analysis.

Design and analysis of a highly efficient coupler between a micro/nano optical fiber and an SOI waveguide.

A compact coupling structure is proposed for highly efficient coupling between a micro/nano fiber and a silicon-on-insulator waveguide. The proposed structure is characterized by high coupling efficiency, wavelength insensitivity, large misalignment tolerance, and easy fabrication. Theoretical analysis and numerical simulation results show that coupling efficiency of >90% can be achieved with a taper length of ∼4.5  μm.

High-Resolution Measurement of Fiber Length Change with Optical Low-Coherence Reflectometer Based on a Fiber-Ring Structure

A simple approach is proposed and experimentally demonstrated to improve measurement precision of short fiber length or fiber length change with an optical low-coherence reflectometer (OLCR). A fiber-ring structure composed of a coupler and a circulator is introduced in the test arm of OLCR to virtually multiply the length of the fiber under test. By measuring the multiplied fiber length under test, the measurement precision is enhanced. A precision enhancement of 10 times is successfully achieved.

Distributed time transfer using optical fiber links

This paper proposes a one point to multi-point distributed time transfer scheme using optical fiber links. The corresponding control protocol and adapters for the proposed scheme are designed and implemented. A 1 to 8 experimental system over 20km single-mode fiber with stabilities less than 50ps is demonstrated.

Frequency transfer over optical fiber based on photonic RF phase shifter

In this paper, an active phase drift cancellation scheme based on a photonic RF phase shifter for frequency transfer over optical fiber is proposed. By this scheme, a linear and stable photonic phase shifter, which is implemented with a dual parallel Mach-Zehnder modulator and an optical filter, is used to compensate the phase drift induced by the fiber transmission. A 1GHz reference signal transfer over 20 km single-mode fiber with sub picosecond timing jitters measured at the remote site is experimentally demonstrated using the proposed scheme.

A new fiber length measuement method with high precision and large absolute length based on FDL

We propose and demonstrate a new fiber length measurement method, which supports large absolute length and high accuracy measurement of fiber. This method is based on multi-stage optical fiber delay lines structure and self-calibration method with Precision Reflectometer. The precision maintains 20 µm and the enlarged measurement range reaches to 6395.43mm.

Transmission-line model for analyzing the coupling between two parallel micro/nano-fibers

The coupling behavior between two parallel micro/nano-fibers is investigated by extending the theory of transmission-lines (TL) to optical domain, Simulation result indicates that the energy transfer length of micro/nano-fibers based coupler is much shorter than that of conventional fiber based coupler. The experiment of the coupling behavior of micro/nano-fibers is demonstrated. It verifies the TL model of micro/nano-fiber coupler. This result may offer valuable reference for the investigation of nano-photonic devices.

SNR of 3-stage fiber delay lines based on SOAs in microwave photonics link

Signal to noise ratio (SNR) of multi-stage optical fiber delay lines based on semiconductor optical amplifiers (SOAs) is demonstrated with experiments by carrying 8 GHz microwave sinusoidal signal. We conclude that, higher input power of microwave source and the higher gain of SOAs will improve the performance of SNR. Whats more, it is shown that more stages of optical fiber delay lines based on SOAs decrease the SNR.

An all-fiber resonator composed of single-channel side-coupled microresonator sequence

An all-fiber resonator composed of single-channel side-coupled microresonator sequence is proposed, in which a sequence of optical fibers, serve as microresonator, and a subwavelength-diameter optical fiber(SDF) with diameter about 1µm is placed along the microresonator perimeter, coupling light into whispering-gallery-modes(WGMs) of the microresonator. The transmission property and dispersion relation are analyzed by transfer matrix method. Infinite sequence structure show band gaps created by Bragg and ring resonances. Finite sequence structure shows a quality factor (Q factor) of 2, 500, a free spectral range (FSR) of 4.7nm and extinction ratio of 5.9dB (one resonator), 6.2dB (two resonator sequence) and 7.8dB (three resonator sequence), respectively. The proposed resonator can be tuned by changing refractive index of microresonator. This device is easy to fabricate and to connect to fiber system.

On polarization characteristic in fiber Mach-Zehnder interferometer with short different length of two arms

Polarization dependent of fiber Mach-Zehnder interferometer is one of the factors which restrict the precision and stability of interferometer based on Mach-Zehnder structure. Making use of Jones Matrix, a propagation equation of polarization dependent fiber Mach-Zehnder interferometer was given, and then the output spectrum was shown by the propagation equation. Then an experimentally result is demonstrated to verify analysis result. It shows the calculating result is consistent with experiment. This result provides a theory guidance to analyze the influence of polarization characteristic in interferometers based on Mach-Zehnder structure. The method also can be adapted in other fiber interferometers such as fiber Michelson interferometer and so on.