Giant Fiber Lasers: A New Paradigm for Secure Key Distribution

We propose and analyze a new concept for secure key distribution based on establishing laser oscillations between the sender and receiver. Compared to quantum mechanics based systems, our scheme allows for significantly higher key-establishing rates and longer ranges. By properly designing the laser structure, it is possible to increase the difficulty of eavesdropping almost arbitrarily, thus making our scheme an intriguing alternative and a complementary technology to quantum key-distribution systems.

Figure 1

GFL system for secure key distribution. $M_A$, $M_B$: Alice’s and Bob’s end mirrors; ${\mathrm{IF}}_A$, ${\mathrm{IF}}_B$: inline filters; ${\mathrm{NS}}_A$, ${\mathrm{NS}}_B$: broadband noise sources. Inset: Frequency response of the three mirrors at the three different states.

Figure 2

Power traces of the left (dotted line) and right (dashed line) propagating waves for various bits selection by Alice and Bob. The link length is $L=10\mathrm{km}$, $K{\gamma }_0=3.2\times {10}^{-4}\mu {\mathrm{m}}^{-1}$, $d=0.1\mathrm{m}$, and $I_{\mathrm{sat}}=10$ [normalized units]. The mirrors are implemented by fiber Bragg gratings with 3 dB bandwidth of $\sim 20\mathrm{GHz}$ and maximal reflection of $\sim 99\%$. The offset between the 1 and 0 mirrors is 4 GHz. The inline filter bandwidth is $\sim 2\mathrm{GHz}$. The power levels are normalized to 1 mW.

Figure 3

Steady-state spectra of the rightward ($A_{+}$) and leftward ($A_{-}$) waves of a GFL with a single inline filter for (a) $\mathrm{\text{Alice}}=“1”$, $\mathrm{\text{Bob}}=“1”$; (b) $\mathrm{\text{Alice}}=“0”$, $\mathrm{\text{Bob}}=“0”$; (c) $\mathrm{\text{Alice}}=“1”$, $\mathrm{\text{Bob}}=“0”$; and (d) $\mathrm{\text{Alice}}=“0”$, $\mathrm{\text{Bob}}=“1”$.

Figure 4

Time trace intensities (a) and steady-state spectra for a GFL with additional (identical) inline filtering for (b) $\mathrm{\text{Alice}}=“1”$, $\mathrm{\text{Bob}}=“1”$; (c) $\mathrm{\text{Alice}}=“1”$, $\mathrm{\text{Bob}}=“0”$; and (d) $\mathrm{\text{Alice}}=“0”$, $\mathrm{\text{Bob}}=“1”$.

Figure 5

Comparison between the key-establishing rates of the QKDS presented in Ref. 10 (dashed line) and the GFL system (solid line). Fiber loss is $\sim 0.3\mathrm{dB}/\mathrm{km}$.