Optical Transceiver Method of QKD Encryption Suite of Technologies
Communications
Optical Transceiver Method of QKD Encryption Suite of Technologies (LEW-TOPS-163)
Space-and-wave division for quantum key distribution photon detection
Overview
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.
The Technology
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.
Benefits
- Enabling: This method allows for the practical application of QKD to free-space optical communication.
- Universal: The methods can be applied to the encryption of any free-space optical communication link.
- Expandability: The system can include additional channels for timing and synchronization duties.
- Hardware Compatibility: The SAW method leverages commercially available double-clad fiber.
- System Simplification: The random bit generator saves cost and complexity by eliminating the need for two additional detectors, simplifying the optics and reducing the amount of data that needs to be stored.
- High-Speed Modulation: The SOA driver allows for high-speed, linear modulation of the laser current, which is not possible with other devices on the market.
- Symmetric Encryption Compatibility: The key conversion process makes variable-length QKD keys usable with standard symmetric encryption strategies, which require fixed key lengths.
Applications
- Satellite-to-ground.
- Satellite-to-satellite.
- Aircraft-to-satellite or aircraft to ground.
- Any free space platform including sea, land, air, or space.
- Other free-space optical communications.
Technology Details
Communications
LEW-TOPS-163
LEW-19920-1
LEW-19913-1
LEW-20058-1
LEW-20224-1
LEW-20119-1
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Similar Results
Secure Optical Quantum Communications
In the prior art, the systems that produced photon pairs took up a great deal of space on a laboratory table, weighed several hundred pounds, consumed tens of kilowatts of electrical power, and required cooling water. These limitations greatly restricted the utility of quantum communications systems, which rely on these photon pairs. To address this issue, Glenn's innovators developed a novel system that uses a laser source, a pair of nonlinear crystals in optical contact with each other, and a fiber coupling point configured to receive a pair of single mode fibers. Pairs of polarization-entangled photons are produced through spontaneous parametric down conversion of the laser beam and provided to the fiber coupling point. The optical signal is coded at the transmitter by modulating the inter-beam delay time between pairs of entangled photons. The inter-beam delay will determine whether the photon pairs are absorbed by a fluorescer in the receiver. When absorbed, the photon pairs cause a fluorescent optical emission that a photon detector identifies. One advantage of this system is that it eliminates the need for a coincidence counter to realize the entanglement-based secure optical communications, because the absorber acts as a coincidence counter for entangled photon pairs. In addition, this modulation spectroscopy technique is ultra-secure since the delay times are very short (femtoseconds) and unresolvable by conventional photon detectors. Finally, the system uses solid-state, monolithic construction that allows for cost-effective batch-manufacturing techniques. This technology represents a significant breakthrough in the fields of communications, optics, cryptography, and surveillance.
Boosting Quantum Communication Efficiency
The technology consists of an array of quantum photon sources connected via a sophisticated switching network. This system is designed to produce single pairs of entangled photons at a high rate while actively suppressing the generation of multiple pairs. The key innovation lies in its ability to detect and eliminate instances where two or more entangled photon pairs are generated, effectively reducing noise in the quantum system.
The technology operates by providing a heralding pulse that notifies the external system of successful entangled photon generation. When multiple pairs are detected, they are prevented from entering the rest of the system, thereby maintaining the integrity of the quantum information.
By combining multiple single-photon sources through its switching network, the technology not only reduces noise but also increases the overall single photon pair generation rate. This dual approach of noise reduction and increased generation efficiency improves qubit transmission rates, potentially by a factor of 10 to 100 over current methods.
While still in the early stages of development, the source array represents a significant advancement in quantum communication systems. It addresses the critical need for high-fidelity entangled photon sources, which are essential for various quantum applications, including entangling sensor networks, quantum computer networks, and quantum key distribution for secure communications.
As quantum technologies continue to evolve, this source array technology positions itself as a crucial component in the development of large-scale, efficient quantum networks, offering a solution to one of the fundamental challenges in quantum information transmission.
Improved High-Speed FPGA Optical Transmitter
For optical modulator drivers, it is important to minimize timing skew in the transmitters to reduce channel distortions. Typical solutions rely on tight tolerances in the design of the path lengths and the use of matched DACs or modulator drivers with built-in channel deskewing provisions. NASA’s novel FPGA design directly drives the optical modulator without DACs or external drivers. This method can reliably align eight 5.76GHz transmitters within 100ps of each other using the built-in transmitter phase interpolator Pulse Position Modulation (PPM) controller and feedback from the optical transceiver.
The algorithm is broken down into sections that iteratively align the transmitter channels, relying on the built-in transmitter phase interpolator PPM controller and feedback from the optical transceiver captured on ADCs connected to the FPGA receiver.
There are three key differentiating components/methods of the NASA technology.
1. The balun network eliminates the need for high-power expensive DACs or modulator driers to generate the multi-level signal required to drive the optics.
2. The use of the FPGA transmitter phase interpolator PPM controller to deskew the channels.
3. The use of a virtual ADC, standard deviation, thresholding, and moving-average processing techniques on loopback data from a QPSK transceiver for the purposes of transmitter channel deskewing.
Optical Tunable-Based Transmitter for Multiple High-Frequency Bands
NASA Glenn's researchers have developed a means of transporting multiple radio frequency carriers through a common optical beam. In contrast to RF infrastructure systems alone, this type of hybrid RF/optical system can provide a very high data-capacity signal communication and significantly reduce power, volume, and complexity. Based on an optical wavelength division multiplexing (WDM) technique, in which optical wavelengths are generated by a tunable diode laser (TDL), the system enables multiple microwave bands to be combined and transmitted all in one unit. The WDM technique uses a different optical wavelength to carry each separate and independent high-frequency microwave band (e.g., L, C, X, Ku, Ka, Q, or higher bands). Since each RF carrier operates at a different optical wavelength, the tunable diode laser can, with the use of an electronic tunable laser controller unit, adjust the spacing wavelength and thereby minimize any crosstalk effect.
Glenn's novel design features a tunable laser, configured to generate multiple optical wavelengths, along with an optical transmitter. The optical transmitter modulates each of the optical wavelengths with a corresponding RF band and then encodes each of the modulated optical wavelengths onto a single laser beam. In this way, the system can transmit multiple radio frequency bands using a single laser beam. Glenn's groundbreaking concept can greatly improve the system flexibility and scalability - not to mention the cost of - both ground and space communications.
Receiver for Long-distance, Low-backscatter LiDAR
The NASA receiver is specifically designed for use in coherent LiDAR systems that leverage high-energy (i.e., > 1mJ) fiber laser transmitters. Within the receiver, an outgoing laser pulse from the high-energy laser transmitter is precisely manipulated using robust dielectric and coated optics including mirrors, waveplates, a beamsplitter, and a beam expander. These components appropriately condition and direct the high-energy light out of the instrument to the atmosphere for measurement. Lower energy atmospheric backscatter that returns to the system is captured, manipulated, and directed using several of the previously noted high-energy compatible bulk optics. The beam splitter redirects the return signal to mirrors and a waveplate ahead of a mode-matching component that couples the signal to a fiber optic cable that is routed to a 50/50 coupler photodetector. The receiver’s hybrid optic design capitalizes on the advantages of both high-energy bulk optics and fiber optics, resulting in order-of-magnitude enhancement in performance, enhanced functionality, and increased flexibility that make it ideal for long-distance or low-backscatter LiDAR applications.
The related patent is now available to license. Please note that NASA does not manufacturer products itself for commercial sale.
