Optical Transceiver Method of QKD Encryption Suite of Technologies

The core of the technology is the SAW division de-multiplexing method (LEW-19920-1). It uses a commercially available double-clad fiber optic cable with a 9um core and a 105um first cladding. By optimizing the wavelengths of the QKD photon and data transmission, a single focusing lens can create a diffraction pattern that directs the QKD photons to the 9um core and the data signal to the 105um secondary core. Key components of the system include: • SOA Driver With Wideband Current Control (LEW-19913-1): This device allows a semiconductor optical amplifier (SOA) or laser to be driven with an arbitrary current at a rate of over 100 MHz. This enables the rapid generation of sub-nanosecond laser pulses with one of four polarization states, which is necessary for QKD. • Random Bit Generator with Linear Feedback Shift Register LFSR Scrambler (LEW-20058-1): This device produces random bits by combining the output of a noise source with a pseudorandom bitstream from the LFSR. This allows a random basis set to be generated on demand for a polarization modulator. • Variable-length quantum key conversion (LEW-20224-1): Since QKD operations produce keys of varying lengths, a strategy was developed to "digest" these raw keys using a hash function, such as SHAKE256. This process generates a fixed-length output that is useful for symmetric encryption schemes like AES256. • The system also incorporates a Discretization Algorithm for Numerical Wave Optics Simulations (LEW-20119-1), which can accurately model the effects of atmospheric turbulence on the propagating optical beam. Overview The process of Quantum Key Distribution (QKD) produces variable length symmetric bit strings at both communication nodes for each QKD operation. This system combines several technologies developed at NASA’s Glenn Research Center to create a secure, practical, and efficient optical transceiver system for QKD. The system uses a Space-And-Wave (SAW) division method to separate low-energy QKD photons from high-energy data transmissions. Unlike traditional methods that use entangled photons, this approach sends and receives encryption keys using weak coherent pulsed light and can be applied to the encryption of any free space optical communications. The technology includes methods for generating a random basis set on demand and for converting variable-length quantum keys into fixed-length keys compatible with mainstream symmetric encryption schemes.