WDM-PON Quantum Encryption with Centralized Detectors
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Solution Overview
Problem
Current quantum key distribution systems face challenges in extending secure communication to a network setting, particularly in passive optical networks (PONs), where bandwidth decreases with the number of users and require expensive single photon detectors for each user, leading to high initial deployment and upgrading costs, as well as increased complexity due to active optical alignment compensation.
Innovation Solution
Implementing a wavelength-division multiplexing (WDM) passive optical network (PON) with a synchronization unit to provide separate classical channels, where single photon detectors are centralized at the server, reducing user-side components and costs, and allowing for easy upgrades, while using a 'plug & play' scheme to minimize channel loss and crosstalk between quantum and classical signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If down-stream key distribution is implemented in TDM-PON, then quantum encryption can be provided to multiple users, but each user requires expensive single photon detectors and bandwidth decreases as number of users increases
Solution Approach 1:
The patent merges the quantum key distribution function with the existing PON infrastructure by integrating quantum channels into the wavelength-division multiplexed network. The server-side quantum transmitter sends quantum signals to multiple users simultaneously through different wavelengths, eliminating the need for each user to have expensive single photon detectors while maintaining quantum encryption capability for all users.
Solution Approach 2:
The patent makes the PON infrastructure universal by enabling it to serve both classical communication and quantum key distribution functions. The existing WDM-PON structure is enhanced to support quantum channels, allowing the network to provide quantum encryption services to multiple users without requiring separate dedicated quantum networks for each user.
2Reliability
If down-stream key distribution is implemented, then quantum encryption can be provided, but upgrading the network requires replacing expensive single photon detectors at each user's location
Solution Approach 1:
The patent extracts the expensive single photon detector requirement from the user-side equipment by implementing a server-based quantum transmitter architecture. The quantum key distribution function is taken out of the user endpoints and centralized at the server, where a single quantum transmitter serves multiple users through wavelength-division multiplexing, eliminating the need for expensive detectors at each user location.
Solution Approach 2:
The patent introduces wavelength-division multiplexing as an intermediary mechanism between the server's quantum transmitter and the users. This intermediary allows multiple users to share the quantum channel efficiently by assigning different wavelengths to different users, enabling network upgrades without replacing expensive single photon detectors at each user endpoint.
3Reliability
If uni-directional key distribution is implemented, then quantum encryption can be provided, but active optical alignment compensation is required which reduces duty cycle and increases operating complexity
Solution Approach 1:
The patent changes the operational parameters by using wavelength-division multiplexing instead of time-division multiplexing for the quantum channel. This parameter change allows simultaneous transmission of quantum signals to multiple users at different wavelengths without requiring active optical alignment compensation, as the wavelengths are passively separated by the optical splitter, thereby simplifying operation and increasing duty cycle.
4Adaptability or versatility
If TDM-PON is used for quantum encryption, then multiple users can share the network, but each user's bandwidth decreases as the number of users increases
Solution Approach 1:
The patent transitions from time-division multiplexing (one dimension) to wavelength-division multiplexing (another dimension). By using different wavelengths for different users simultaneously, the system achieves multi-user support without sacrificing individual user bandwidth, as each user receives dedicated wavelength channels that do not share the time resource.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a cost-efficient, user-friendly QKD system with minimal calibration needs, capable of high-speed operation, robustness against environmental changes, and compatibility with classical data communication, allowing users to switch between quantum and classical communication without interfering with other users, and reducing backscattering and leakage issues.
Implementation Method 1
use the wavelength-division multiplexing (WDM) technique... Each transmitter has a dedicated ONU 14. The signals from all the transmitters are combined into the same channel with a WDM 24
Implementation Method 2
The data stream is passively routed to ONUs 14 using techniques such as the Time Domain Multiplexing (TDM), the Wavelength Domain Multiplexing (WDM)... The data stream broadcasted by the OLT is passively splitted by an optical splitter
Implementation Method 3
Down-stream key distribution requires that each user possesses a pair of single photon detectors (SPDs)
Implementation Method 4
a synchronization unit having a second WDM-PON to synchronize with the first WDM-PON and to provide separate classical channels for data communication
Implementation Method 5
using a 'plug & play' scheme to minimize channel loss and crosstalk between quantum and classical signals
Data Source
AI summary
Systems and methods to communicate securely includes communicating quantum encryption data on a first wavelength-division multiplexing passive optical network (WDM-PON); and communicating data over separate classical channels of a second WDM-PON, wherein the second WDM-PON synchronizes with the first WDM-PON while providing data communication over the classical channels.