Andrew R. Grant

Suppression of intrachannel nonlinear effects with alternate-polarization formats

We investigate using alternate-polarization (APol) on-off keying formats, in which adjacent bits have orthogonal states of polarization, to suppress intrachannel nonlinear impairments in dispersion-managed (DM) optical fiber transmission systems. Simple methods to generate the APol formats are discussed, and the transmission performance of the APol formats for both 40-Gb/s DM systems and 10-Gb/s DM-soliton systems is experimentally studied. We show that the APol formats can significantly improve the performance of 40-Gb/s DM transmission systems, while the improvement of 10-Gb/s systems is smaller.

Calculating the Raman pump distribution to achieve minimum gain ripple

A procedure is presented for calculating the optimum Raman pump wavelengths and powers for a discrete set of lasers and for a pump continuum. Theoretical results in the continuum case shown that broad-band gain with extremely low ripple can be obtained.

A novel method for synchronizing the pulse carver and electroabsorption data modulator for ultralong-haul DWDM transmission

The authors demonstrate a novel solution to detect and correct the temporal misalignment between the pulse carver and electroabsorption modulator for ultralong-haul dense wavelength-division-multiplexing transmission. The correct timing is achieved by minimizing the chirp of the optical data pulses. The technique is independent of the bit rate and channel spacing and can be implemented at low cost. The device can also be used as a wavelength locker. The use of electroabsorption modulators for ultralong-haul transmission is validated with a 5000-km 10-Gb/s soliton system experiment.

Performance degradation due to polarization effects in a dispersion-managed-soliton recirculating loop system

We investigate the performance degradation in dispersion-managed soliton systems caused by polarization-dependent loss and polarization-mode dispersion using a 600-km recirculating loop. We show that in an ultralong-haul transmission system, polarization effects can easily induce a variation in the bit-error rate (BER) greater than two orders of magnitude. In addition, polarization scattering caused by soliton collisions in wavelength-division-multiplexing systems makes the polarization-induced BER variation smaller than that in single-channel systems.

A novel method for synchronizing the pulse carver and electroabsorption data modulator in RZ optical transmitters

In conclusion, we demonstrated a device to detect and correct the timing misalignment between the pulse carver and electroabsorption data modulator in a RZ transmitter. The device can be used for all the channels on the ITU grid. It is straightforward to modify the design of the device to work for a different bit-rate. The implementation of the device can be done at low cost. The device can also be used as a wavelength locker. We demonstrated that the EAM is viable as a data modulator even for ULH transmission. With the facile synchronization scheme the EAM affords, it should be even more attractive as a transmitter for future transmission systems.

Agile optoelectronic fiber sources for hyperspectral chemical sensing from SWIR to LWIR

The use of optical frequency combs (OFCs) for multi-heterodyne spectroscopy has enabled unprecedented measurement capabilities for spectroscopic sensing, including rapid acquisition speed, high resolution and high sensitivity1,2. Development of field deployable OFC sources that are widely tunable in the important chemical fingerprint region in the long-wavelength infrared (LWIR) is a major research challenge. In this paper, we report our recent efforts towards developing LWIR comb source for SILMARILS (Standoff ILluminator for Measuring Absorbance and Reflectance Infrared Light Signatures) program by IARPA. LGS has developed fiber optic sources producing spectral combs in the SWIR (1.52 to 1.56 μm and 1.7 to 2.0 μm) and in the LWIR (7.7 to 12.1 μm) regions. The spectral combs in the LWIR are generated by difference-frequency mixing one OFC centered around 1.54 μm with another OFC, whose center wavelength is tunable between 1.7 and 2.0 μm, in a nonlinear optical crystal. Average power of the generated LWIR is 1.2-12 mW and its instantaneous spectral breadth of the combs is > 80 cm-1, sufficiently broad to cover multiple molecular absorption peaks. We demonstrate standoff sensing of chemical targets having concentration as low as 12 μg/cm2 by measuring LWIR transflectance spectra using the comb source.

Demonstration of dense WDM over more than > 20,000 km, using dispersion-managed solitons and novel, periodic-group-delay-complemented dispersion compensation

In an all-Raman amplified, recirculating loop containing 100 km spans, each compensated 80% by DCF and 20% by an efficient PGD (periodic-group-delay) device, we have demonstrated 10G dense WDM, over >20,000 km. The novel dispersion compensation causes drastic reduction of collision-induced timing jitter.