Raymond M. Sova

Tunable dual-wavelength all-PM fiber ring laser

A multisegment all-PM fiber ring laser is constructed to demonstrate a tunable dual-wavelength laser source with continuous tuning in absolute wavelength and discrete tuning in wavelength spacing. The tuning method is based on birefringence filtering properties of a segmented all-PM fiber ring resonator. Using this method, we show a discrete wavelength spacing of dual-wavelength output from 0.9 to 2.5 nm, and continuous wavelength tuning over a few nanometers. The demonstrated dual-wavelength laser can be easily modified to tune over a greater wavelength spacing and absolute wavelength range.

Tunable multi-wavelength all-fiber Raman source using fiber Sagnac loop filter

A multi-wavelength source is demonstrated in a cascaded-Raman fiber ring laser configuration using a tunable dual-section high birefringence fiber Sagnac loop filter. Depending on the pump powers and the cavity configurations, the source operates in the different wavelength regime between the 1120 and 1580 nm via cascaded Raman Stokes generation. The source generate up to 20 wavelength channels within the different orders of Raman Stokes wave regime with 0.4 nm channel spacing. The channel separation and the absolute wavelength of the multi-wavelength output are tunable and we show a discrete wavelength spacing of multi-wavelength output from 0.4 to 3 nm and continuous wavelength tuning over the wavelength channel spacing.

Optical fiber modal birefringence measurement based on Lyot-Sagnac interferometer

We propose and demonstrate a simple and accurate optical fiber modal birefringence measurement technique based on a two-segment Lyot-Sagnac fiber interferometer. We have conducted accurate measurements for several low birefringence fibers and the results are consistent with published data. This measurement method is allowed in the birefringence-length product ranging from 10/sup -3/ to 10/sup -6/ m within the resolution of the optical spectrum analyzer used.

Requirements and challenges for tactical free-space Lasercomm

Mobile free-space laser communications is the next frontier for net-centric connectivity, as bandwidth, spectrum and security issues drive its adoption as an adjunct to RF communications. However, key technology challenges must be addressed and mission requirements understood for it to emerge as a meaningful capability for dynamic tactical communications environments. We present a brief overview of the current military communication infrastructure and future needs, before highlighting terrestrial Lasercomm technology status and trends, and lessons learned from several experiments and field tests. Optical link service parameters and metrics are assessed in the context of available architecture and techniques, while the effectiveness of various technologies to mitigate atmospheric turbulence, poor weather and pointing/tracking inaccuracies is analyzed for improved reliability. Finally, the ramifications of cost and SWaP (size, weight and power), critical to tactical Lasercomm deployment, are considered in narrowing down these technology options.

80 Gb/s free-space optical communication demonstration between an aerostat and a ground terminal

A free-space optical (FSO) communication demonstration was conducted with JHU/APL and AOptix at the TCOM Test Facility in Elizabeth City, NC in May 2006. The primary test objective was to evaluate the performance of an FSO link from a fiber-tethered aerostat to a ground platform at effective data rates approaching 100 Gigabits/sec using wavelength division multiplexing (WDM) techniques. (Multiple optical channels operating near 1550 nm were modulated at data rates of 1, 10 and 40 Gbps). The test was conducted with a 38 meter aerostat raised to an altitude of 1 km and a ground platform located 1.2 km from the aerostat (limited by property boundary). Error free data transfers of 1.2 Terabits in 30 seconds at 40 Gbps were demonstrated. The total data transferred during the test was greater than 30 Terabits with an average BER of 10-6 without any forward error correction (FEC) coding.

Tunable all-fiber birefringence comb filters

We have demonstrated a novel all-fiber comb filter with adjustable channel spacing. The filter can be used as an element in a multi-wavelength laser and provide great flexibility in laser design. Both Lyot and Sagnac-Lyot filters have been demonstrated. The Lyot filter provides a large number of wavelength spacings with only a few fiber segments. (e.g. 40 spacings for 4 segment filter) whereas the Sagnac-Lyot filter provides a tunable filter function that is independent of input polarization. Typical values of measured insertion loss were 4 dB and extinction ratio of 15 dB. The insertion loss values can be improved by using low-loss polarization controllers and improving the fusion splicing of the PM/non-PM fiber splices.

Dual-Wavelength Brillouin Fiber Laser for Microwave Frequency Generation

We demonstrate generation of RF/microwave frequencies using a dual-wavelength Brillouin fiber laser. We propose this device as a potential source of low phase noise, tunable frequencies into the millimeter wave regime compatible with RF-photonic systems.

Long distance laser communications demonstration

AOptix demonstrated a simulated air-to-air laser communications (laser-com) system over a 147Km distance by establishing a laser communication link between the islands of Hawaii and Maui. We expect the atmospheric conditions encountered during this demonstration to be representative of the worst seeing conditions that could be expected for an actual air to air link. AOptix utilized laser-com terminal incorporating Adaptive Optics (AO) to perform high speed tracking and aberration correction to reduce the effects of the seeing. The demonstration showed the feasibility of establishing high data rate point to point laser-com links between aircraft. In conjunction with Johns Hopkins University Applied Physics Laboratory networking equipment we were able to demonstrate a 40Gbit DWDM link, providing significantly more data throughput than is available using RF technologies. In addition to being very high data rate, the link demonstrates very low beam spread, which gives very high covertness, and a high degree of data security. Since the link is based on 1550nm optical wavelengths it is inherently resistant to jamming.

Demonstration of high-data-rate wavelength division multiplexed transmission over a 150-km free space optical link

A 150 km free-space optical (FSO) communication link between Maui (Haleakala) and Hawaii (Mauna Loa) was demonstrated by JHU/APL and AOptix Technologies, Inc. in September 2006. Over a 5 day period, multiple configurations including single channel 2.5 Gbps transmission, single channel 10 Gbps, and four wavelength division multiplexed (WDM) 10 Gbps channels for an aggregate data rate of 40 Gbps were demonstrated. Links at data rates from 10 to 40 Gb/s were run in excess of 3 contiguous hours. Data on the received power, frame synchronization losses, and bit error rate were recorded. This paper will report on the data transfer performance (bit error rates, frame synchronization issues) of this link over a 5 day period. A micropulse lidar was run concurrently, and on a parallel path with the FSO link, recording data on scattering loss and visibility. Comparisons between the state of the link due to weather and the data transfer performance will be described.

Demonstration of dual-polarization fiber ring laser for microwave generation

We demonstrate a photonic technique for the tunable generation of RF, microwave and millimeter wave signals with a single optical source. A dual-polarization supporting and maintaining fiber ring laser is constructed and its use as a tunable RF source is demonstrated.