We present a symmetric physical layer based secret key generation scheme for Point-to-Point Optical Link (PPOL) communication by exploiting Polarization Mode Dispersion (PMD) as a random and inimitable channel characteristic. The randomness and security strength of generated cryptographic keys based on PMD is significantly high. In this paper, we present that random modulation of a probe signal caused by PMD in a high-speed data communication network (40 Gb/s and 60 Gb/s) is reciprocal with average Pearson correlation coefficient of 0.862, despite the presence of optical nonlinearities, dispersion, and noise in the system. 128-bit symmetric cryptographic key has been successfully generated using the proposed scheme. Moreover, PMD-based encryption keys passed the National Institute of Standards and Technology (NIST) tests. We have shown through simulations with a 50 km link that, with optimal key generation settings, symmetric keys can be generated with high randomness (high P-values for NIST randomness tests) and with sufficient generation rates (>50%). Furthermore, we considered an attack model of a non-invasive adversary intercepting at 10 km into the link and found that the generated keys have high average key bit mismatch rates (>40%).

The pointing jitter originated from the random mechanical vibration of the optical platform and the noise associated with the optomechanical sensor system unquestionably deteriorate the performance of the inter-satellite optical link. The impact of the jitter changes significantly with the receiver architecture. In this paper, we present a mathematical model to investigate the link performance in the presence of angular pointing jitters for different receiver architectures. Alongside the statistical pointing error model, the derived model incorporates key receiver design parameters such as detector radius, receiver aperture size, f -number of the lens system, and beam compression ratio to study the impact of receiver architecture on the pointing jitter. As an example, a CubeSat optical receiver is analyzed. We show that by careful selection of beam compression ratio and f -number, more than 5 orders of magnitude bit error rate improvement is achievable even at large pointing error.

We have developed a multi-tone modulated continuous wave (MTCW) Lidar system made of a CW laser with multiple fixed RF tones for a high precision range finding and velocimetry. In this paper, the MTCW Lidar system has been studied analytically and numerically. A proof-of-concept experiment by employing 1550nm light source and multiple RF tone modulations ranging from 50MHz to 6GHz has been performed to demonstrate proof of principle for range finding with <1cm range resolution. We also provide sine fitting algorithms on the measured RF tones to extract the range information in a single shot RF measurement and demonstrate the ways to improve the resolution beyond the actual RF bandwidth.

An efficient omnidirectional CubeSat data crosslink is imperative to ensure the success of resource-intensive advanced CubeSat missions. In this article, we present a feasibility study of wireless technologies in high-speed CubeSat crosslink design. We study the power consumption, pointing requirement, and antenna requirement of each technology to implement an omnidirectional communicator. We also investigate the performance limit of the state-of-the-art wireless technologies considering the realizable link parameters. The achievable data rate and communication distance are studied thoroughly for different communication systems. The analyses show that an optical communication link is capable of delivering more than two orders of magnitude higher data throughput than that of microwave links in an omnidirectional platform. However, the study shows that due to the size and power restriction, a performance crossover region exists where the performance of a microwave channel exceeds the performance of the optical channel. The crossover distance and crossover data rate are studied thoroughly with different system configurations and modulation formats to assess the maximum reach of wireless technologies in a CubeSat crosslink.

CubeSat swarm in low earth orbit is an attractive alternative to present-day expensive and bulky satellite-based remote sensing systems. This article presents the design and optimization rules to achieve omnidirectional, high speed, long-range (more than 100 km) data communication among CubeSats. The unprecedented size, weight, power, and cost constraints imposed by the CubeSat platform and the availability of the commercial-off-the-shelf components are considered in the analyses. Analytical studies related to the scanning mirror based beam steering system as well as scanning mirror's smallest step angle requirement are presented. In addition, we demonstrate the relations and dependencies among scanning mirror's smallest step angle, laser beam divergence, optics dimensions, communication distance, and scanning area filling efficiency, etc. Furthermore, the optimization challenges of the transmit laser beam size considering the interplay among beam divergence, beam clipping, and scattering are studied in detail. This article also presents the effect of laser peak power, initial beam size, and communication distance on effective communication beamwidth to maintain a long-distance (more than 100 km) communication with SNR ≥ 10 dB at a data rate greater than 500 Mb/s.

Advanced space missions e.g. interplanetary exploration and earth observation embrace constellation or swarm-like CubeSat configuration to achieve unprecedented spatial and temporal resolutions at a significantly lower investment. The realization of high-speed inter CubeSat data communication link is mandatory to ensure the success of such missions. In this paper, we present a scalable high-speed CubeSat crosslink implementation based on Wavelength Selective Optical Transceiver (WSOT) design. System performance based on the state-of-the-art components that satisfy the stringent size, weight, power, and cost requirements has been investigated. We estimate that with a 15 mm transceiver aperture size and 1 W peak bit power, the system attains communication distance up to 125 km and 80 km for 400 Mb/s and 800 Mb/s data rates, respectively. Additionally, we present optical and mechanical design of five transceiver units that can fit inside a 3 U CubeSat to achieve full field of regard (360o) to enable omnidirectional high-speed optical communication. Further performance improvements are possible through incorporating advanced amplifiers, error correction coding, and large aperture optics.