Shaif-ul Alam

73.7 Tb/s (96 x 3 x 256-Gb/s) mode-division-multiplexed DP-16QAM transmission with inline MM-EDFA

Transmission of a 73.7 Tb/s (96 x 3 x 256-Gb/s) DP-16QAM mode-division-multiplexed signal over 119 km of few-mode fiber transmission line incorporating an inline multi mode EDFA and a phase plate based mode (de-)multiplexer is demonstrated. Data-aided 6 x 6 MIMO digital signal processing was used to demodulate the signal. The total demonstrated net capacity, taking into account 20% of FEC-overhead and 7.5% additional overhead (Ethernet and training sequences), is 57.6 Tb/s, corresponding to a spectral efficiency of 12 bits/s/Hz.

Thulium-doped fiber amplifier for optical communications at 2 µm

We report the realization of a thulium doped fiber amplifier designed for optical communications providing high gain (>35dB) and low noise figure (<;6dB) over 1910nm-2020nm with a maximum saturated output power of more than 1W.

Picosecond fiber MOPA pumped supercontinuum source with 39 W output power

We report picosecond fiber MOPA pumped supercontinuum source with 39W output, spanning at least 0.4–1.75µm with high and relatively uniform spectral power density of ∼31.7mW/nm corresponding to peak power density of ∼12.5W/nm in 20ps pulse.

High power pulsed fiber MOPA system incorporating electro-optic modulator based adaptive pulse shaping

We demonstrate active pulse shaping using an Electro-Optic Modulator in order to compensate the pulse shaping effects caused by Gain Saturation in a high power Yb doped fiber amplifier chain and to generate various custom-defined output pulse shapes. Square, step and smooth pulse shapes are achieved, with mJ pulse energies. Use of a modulator to shape pulses rather than direct modulation of the diode drive current allows us to eliminate undesired transients due to laser start up dynamics. The required shaping is calculated based on a simple measurement of amplifier performance, and does not require detailed modeling of the amplifier dynamics.

First demonstration and detailed characterization of a multimode amplifier for space division multiplexed transmission systems

We present the first demonstration of a multimode (two mode-group) erbium-doped fiber amplifier for Space Division Multiplexed (SDM) applications and demonstrate various design and performance features of such devices. In particular we experimentally demonstrate that differential modal gains can be controlled and reduced both by fiber design and control of the pump field distribution. Using a suitably designed fiber we demonstrate simultaneous modal gains of ~20 dB for different pair-wise combinations of spatial and polarization modes in an EDFA supporting amplification of 6 distinct modes.

Demonstration of amplified data transmission at 2 µm in a low-loss wide bandwidth hollow core photonic bandgap fiber

The first demonstration of a hollow core photonic bandgap fiber (HC-PBGF) suitable for high-rate data transmission in the 2 µm waveband is presented. The fiber has a record low loss for this wavelength region (4.5 dB/km at 1980 nm) and a >150 nm wide surface-mode-free transmission window at the center of the bandgap. Detailed analysis of the optical modes and their propagation along the fiber, carried out using a time-of-flight technique in conjunction with spatially and spectrally resolved (S2) imaging, provides clear evidence that the HC-PBGF can be operated as quasi-single mode even though it supports up to four mode groups. Through the use of a custom built Thulium doped fiber amplifier with gain bandwidth closely matched to the fibers low loss window, error-free 8 Gbit/s transmission in an optically amplified data channel at 2008 nm over 290 m of 19 cell HC-PBGF is reported.

Mid-infrared ZBLAN fiber supercontinuum source using picosecond diode-pumping at 2 µm

We present the first demonstration of mid-IR supercontinuum generation directly pumped with picosecond pulses from a Thulium fiber-amplified gain-switched laser diode at 2 µm. We achieve more than two octaves of bandwidth from 750 - 4000 nm in step-index ZBLAN fiber with Watt-level average power and spectral flatness of less than 1.5 dB over a 1300 nm range in the mid-IR from 2450 - 3750 nm. The system offers high stability, power-scaling capability to the 10 W regime, and demonstrates an attractive route towards relatively inexpensive, versatile and practical sources of high power broadband mid-IR radiation.

8- and 16-channel all-fiber DFB laser WDM transmitters with integrated pump redundancy

All-fiber DFB-laser-based 8-channel 100-GHz and 16-channel 50-GHz wavelength-division-multiplexing (WDM) transmitter arrays with integrated pump redundancy are demonstrated for the first time. Each fiber laser WDM channel in the modules remain in operation despite the drop out of several of the pump diodes and the maximum power drop to each channel in an 8/spl times/8 channel 100-GHz system for the drop of seven out of eight pump diodes is just 14 dB.

Diode-pumped wideband thulium-doped fiber amplifiers for optical communications in the 1800 - 2050 nm window

We present the first in-band diode-pumped TDFAs operating in the 2 µm wavelength region and test their suitability as high performance amplifiers in potential future telecommunication networks. We demonstrate amplification over a 240 nm wide window in the range 1810 - 2050 nm with up to 36 dB gain and noise figure as low as 4.5 dB.

100 kW peak power picosecond thulium-doped fiber amplifier system seeded by a gain-switched diode laser at 2 μm

We report on the generation of picosecond pulses at 2 μm directly from a gain-switched discrete-mode diode laser and their amplification in a multistage thulium-doped fiber amplifier chain. The system is capable of operating at repetition rates in the range of 2 MHz-1.5 GHz without change of configuration, delivering high-quality 33 ps pulses with up to 3.5 μJ energy and 100 kW peak power, as well as up to 18 W of average power. These results represent a major technological advance and a 1 order of magnitude increase in peak power and pulse energy compared to existing picosecond sources at 2 μm.