Ming-Jun Li

Mode-division multiplexed transmission with inline few-mode fiber amplifier

We demonstrate mode-division multiplexed WDM transmission over 50-km of few-mode fiber using the fibers LP01 and two degenerate LP11 modes. A few-mode EDFA is used to boost the power of the output signal before a few-mode coherent receiver. A 6×6 time-domain MIMO equalizer is used to recover the transmitted data. We also experimentally characterize the 50-km few-mode fiber and the few-mode EDFA.

Ultra-Low Bending Loss Single-Mode Fiber for FTTH

A new ultra-low bending loss single-mode fiber with ring comprising nanometer sized features is designed and manufactured. Bending loss less than 0.1 dB/turn at 1550 nm and a bend radius of 5 mm is demonstrated. Other optical parameters of the fiber are fully compatible the standard telecommunications grade single-mode fibers.

1.05Pb/s Transmission with 109b/s/Hz Spectral Efficiency using Hybrid Single- and Few-Mode Cores

We demonstrated 1.05-Pb/s transmission over 3km of multicore fiber with spectral efficiency of 109b/s/Hz, using twelve single-mode cores carrying DP-32QAM-OFDM signals and two few-mode cores carrying DP-QPSK in their LP01 and two LP11 modes.

Brillouin gain analysis for fibers with different refractive indices

We studied an anomalous result in the measured stimulated Brillouin scattering threshold for single-mode optical fibers with different refractive index profiles and effective areas. It was found that, in addition to the optical effective area, the refractive-index-dependent interaction between the optical and the acoustic fields must be considered in order to account for the differences in the stimulated Brillouin scattering threshold between fiber types. A detailed analytical formalism describing the acousto-optic interaction was derived to accommodate the influence of the index profile design on Brillouin scattering.

Fibers with low polarization-mode dispersion

Fibers with low polarization-mode dispersion (PMD) enable high-bit-rate time-division-multiplexed optical communication systems. These fibers are becoming increasingly important with the growing implementation of wavelength-division-multiplexing (WDM) transmission with channel bit rates of 40 Gb/s. Important to the realization of low PMD fibers are the fibers index and stress profiles, polarization-mode coupling, and the evolution of the polarization state with length. This paper reviews recent progress in the understanding of the fabrication and characteristics of these fibers. The paper also discusses the important fiber physical parameters, including the fiber index profile and fiber spinning parameters and their impacts on the realization of low PMD performance.

Single-polarization fiber with a high extinction ratio.

An elliptical-core hole assisted single-polarization fiber was designed, fabricated, and characterized. Numerical modeling based on the vectorial Maxwell equation reveals the dependence of the single-polarization bandwidth on core delta and air-hole size. Several single-polarization fibers based on this design with their single-polarization operating windows centered between 0.9 and 1.5 microm were successfully demonstrated. A correlation between fiber birefringence and single-polarization operating bandwidth is qualitatively confirmed. A single-polarization bandwidth as high as 55 nm was observed. These fibers also show very high extinction ratios of 60 dB or higher at lengths much shorter than 1 m. Other properties such as the dependence on length of the single-polarization operating window were also measured.

Nonlinear fibers for signal processing using optical Kerr effects

This paper reviews nonlinear optical-fiber designs for signal processing using optical Kerr effects. The requirements for designing nonlinear fibers are described first. Then, the design concept is discussed and design examples are shown to illustrate the tradeoffs among the different fiber properties such as effective area, dispersion, and attenuation. Furthermore, fiber designs with distributed Brillouin frequency shift to mitigate the effect of simulated Brillouin scattering (SBS) in nonlinear fibers are discussed in detail. An SBS-threshold increase of 7 dB over conventional nonlinear fibers is experimentally demonstrated.

High bandwidth single polarization fiber with elliptical central air hole

A novel design of single polarization fiber is presented. The structure of the fiber comprises an elliptical central air hole with depressed cladding surrounding the core. Parameters that affect the performance of the single polarization fiber in terms of the location of the single polarization operating window and single polarization bandwidth are analyzed. The analysis results in the identification of a fiber design that can yield a single polarization bandwidth as high as 240 nm around 1550 nm.

Highly birefringent hollow-core photonic bandgap fiber

A highly birefringent hollow-core photonic bandgap fiber is fabricated and characterized. The fiber group birefringence is found to be 0.025 at 1550 nm through wavelength scanning method and direct measurement of differential group delay.

Suppression of Raman gain in single-transverse-mode dual-hole-assisted fiber.

Measurements of backscattered Raman amplified spontaneous emission in single-mode dual-hole-assisted fiber indicate suppression of Raman gain by more than two orders of magnitude compared to SMF. These results imply that fiber lasers based on the dual-hole-assisted fiber design are effectively immune to SRS, thus enabling significant power scaling beyond current limits from a single-mode core.