Cang Jin

10-Mode mode-multiplexed transmission over 125-km single-span multimode fiber

We demonstrate combined wavelength- and mode-multiplexed transmission over a 125-km multimode single span composed of 10- and 15-mode fibers with a spectral efficiency of 29 b/s/Hz. A transmission capacity of 115.2 Tb/s is achieved over a distance of 87 km.

Integrated cladding-pumped multicore few-mode erbium-doped fibre amplifier for space-division-multiplexed communications

Multicore, few-mode fibre amplifier boosts 18 spatial channels simultaneously for higher data transmission capacity.

Tailored modal gain in a multi-mode erbium-doped fiber amplifier based on engineered ring doping profiles

Various space division multiplexing (SDM) schemes are currently investigated as a way to overcome the capacity limit of data links. We here focus on mode division multiplexing (MDM) in a multi-mode fiber (MMF). Towards long-haul data transmission, for which signal amplification is a key enabling component, we investigate a simple approach to precisely control the mode-dependent gain (MDG) between the co-propagating LP01 and LP11 modes of an erbium-doped few-mode fiber amplifier (MM-EDFA) by engineering a multi-ring doping profile. In practice, the mode dependent loss of the few-mode transmission fiber must be taken into account in order to equalize the gain for all modal channels. In a step towards practical implementation of MM-EDFA for long-haul SDM, we extend the single ring doping approach to incorporate multi-ring and multi-level doping. Through numerical simulations we study the optimization of the width and doping level of each ring so as to control the MDG. We further discuss the possibility of modal gain equalization through zero-differential modal gain (ZDMG) points in a single stage MM-EDFA, or via tuning of pump powers in a dual-stage MM-EDFA configuration.

Efficient annular cladding amplifier with six, three-mode cores

We demonstrate a multi-core, multi-mode optical amplifier with 18 spatial channels pumped by a single 15-W multi-mode pump diode. The amplifier has >20-dB gain per mode, <;3-dB mode and core dependent gain, and >31 mW per spatial channel.

Complete Dispersion Characterization of Few Mode Fibers by OLCI Technique

Few-mode optical fibers (FMFs) are useful for many applications such as space-division-multiplexing (SDM), high laser power generation and transport, dispersion compensation, etc. The emergence of SDM induces considerable requirements in terms of FMF characterization (chromatic dispersion, birefringence, modal content, bending losses). All LP modes of an FMF can be simultaneously characterized using phase-sensitive optical low-coherence interferometry. The differential modal group delay and absolute chromatic dispersion values of each mode are retrieved from a single measurement without spatial mode transformers.

Demonstration of Cladding-Pumped Six-Core Erbium-Doped Fiber Amplifier

We demonstrate cladding-pumped six-core Erbium-doped fiber amplifiers (EDFAs) using two different pump coupling schemes: edge-coupled and side-coupled pumping, where a single multimode laser diode can be applied to pump all cores. Using two in-line cladding-pumped EDFAs at the input and output of a 31-km coupled-six-core fiber, we realized 465-km space-division multiplexing and wavelength division multiplexing transmission in a recirculating loop and achieved a spectral efficiency of 18 bits/s/Hz. Through side-coupled pumping, the cladding-pumped six-core EDFA produced >18-dBm output power per core and had <;6-dB noise figure across the C-band.

Annular-cladding erbium doped multicore fiber for SDM amplification

An annular cladding ED-MCF is proposed to enhance pump power efficiency. Simulations suggest amplification with over 29 dB gain and less than 7.5 dB noise figure at 1550 nm using a single Watt-level pump.

Microwave interferometric technique for characterizing few mode fibers

We propose and experimentally demonstrate a simple and accurate technique for measuring differential mode group delay (DMGD) in few mode fibers (FMF). A frequency-swept microwave signal is modulated on a filtered optical incoherent source. The microwave signals carried on different fiber modes experience different time delays and interfere with each other in the photodetector. Optical interference between propagating fiber modes is avoided by the use of an incoherent optical source. A mathematical model is established to analyze the interference pattern and extract the DMGD values. A 456-m two-mode fiber and a 981-m FMF, which supports four LP modes, are measured. The measurement covers the whole C-band and the results coincide well with those obtained by the time-of-flight method and the numerical simulations. A precision of ±0.002 ps/m is achieved.

Characterization of few mode fibers by OLCI technique

All LP modes of a few mode fiber are simultaneously characterized using phase-sensitive optical low-coherence interferometry. The differential modal group delay and absolute chromatic dispersion values of each mode are retrieved from a single measurement without spatial mode transformers.

Demonstration of an erbium-doped fiber with annular doping for low gain compression in cladding-pumped amplifiers

We present the design and characterization of a cladding-pumped amplifier with erbium doping located in an annular region near the core. This erbium-doped fiber is proposed to reduce gain saturation, leading to smaller gain compression when compared to uniform core doping. Through numerical simulations, we first compare the performance of three fibers with different erbium doping profiles in the core or the cladding. When the doped fibers are operated at the optimum length, results show that the smaller overlap of the signal mode field with the annular erbium doping region leads to higher gain and lower saturation of the amplifier. A single-core erbium-doped fiber with an annular doping and a D-shaped cladding was fabricated. Measurements demonstrate less than 4 dB of gain compression over the C-band for input power ranging from -40 dBm to 3 dBm. Small gain compression EDFAs are of interest for applications that require input channel reconfiguration. Higher gain and saturation output power are also key issues in cladding-pumped multi-core amplifiers.