Private and secure optical communication system using an optical tapped delay line
A method and apparatus for secure transmission of an information-containing optical signal. An optical signal is divided into a first plurality of sub-bands. Each of the sub-bands is modified to encrypt the information contained in the optical signal. The modified sub-bands are combined into a combined optical signal. The combined optical signal is divided into a second plurality of sub-bands. Each of the second plurality of sub-bands is modified to decrypt the previously encrypted information contained in the optical signal.
1. A method for secure transmission of an information-containing optical signal in a reflective/transmissive architecture, comprising:
dividing the optical signal using an optical tapped delay line into a first plurality of spectral sub-bands defined by the equation:
F
(
t
,
K
)
=
∫
ω
K
ω
K
+
1
∫
0
T
f
(
S
+
t
)
ⅇ
jωS
ⅆ
S
ⅆ
ω
where
i. t=aperture of the hyperfine device (tap key),
ii. S=time integration variable,
iii. ω=frequency, and
iv. K=sub-band index,
modifying each of the first plurality of spectral sub-bands to encrypt the information contained in the optical signal by at least one of (i) imparting a phase shift to each sub-band, (ii) imparting a time delay to each sub-band, and (iii) imparting a frequency shift to each sub-band,
combining the modified first plurality of spectral sub-bands into a combined optical signal,
dividing the combined optical signal into a second plurality of spectral sub-bands,
modifying each of the second plurality of spectral sub-bands to decrypt the previously encrypted information contained in the optical signal by at least one of (i) imparting a phase shift to each sub-band, (ii) imparting a time delay to each sub-band, and (iii) imparting a frequency shift to each sub-band.
2. The method of claim 1 wherein the information-containing optical signal has a bandwidth and at least one of the first and second plurality of spectral sub-bands has a sub-band resolution at least 50 times finer than the bandwidth of the information-containing optical signal.
3. The method of claim 1 wherein the information-containing optical signal is transmitted at a bit rate of not less than 1 gigabit per second.
4. The method of claim 1 wherein the information-containing optical signal is transmitted at a bit rate of not less than 10 gigabits per second, wherein at least the first plurality of spectral sub-bands comprise not less than 50 spectral sub-bands and wherein at least the first plurality of spectral sub-bands has a spatial resolution at a focal plane of not greater than 200 MHz.
5. The method of claim 1 wherein the first plurality of spectral sub-bands comprise not less than 100 spectral sub-bands.
6. The method of claim 1 wherein at least one of the steps of modifying each of the first plurality of spectral sub-bands and modifying each of the second plurality of spectral sub-bands comprises at least one of imparting a phase shift to each sub-band, imparting a time delay to each sub-band, and imparting a frequency shift to each sub-band.
7. The method of claim 6 comprising at least one of imparting a phase shift to each sub-band, imparting a time delay to each sub-band, and imparting a frequency shift to each sub-band at a rate that changes over time.
8. The method of claim 1 comprising imparting a frequency shift to the information-containing optical signal.
9. A system for secure transmission of an information-containing optical signal, comprising:
at least a first optical tapped delay line configured to enable division of the optical signal into a first plurality of spectral sub-bands defined by the equation:
F
(
t
,
K
)
=
∫
ω
K
ω
K
+
1
∫
0
T
f
(
S
+
t
)
ⅇ
jωS
ⅆ
S
ⅆ
ω
where
v. t=aperture of the hyperfine device (tap key),
vi. S=time integration variable,
vii. ω=frequency, and
viii. K=sub-band index,
at least a first phase modulator configured to enable modification of each of the first plurality of spectral sub-bands to encrypt the information contained in the optical signal by at least one of (i) imparting a phase shift to each sub-band, (ii) imparting a time delay to each sub-band, and (iii) imparting a frequency shift to each sub-band, the first optical tapped delay line being configured to enable combining the modified first plurality of spectral sub-bands into a combined optical signal,
at least a second optical tapped delay line configured to enable division of the combined optical signal into a second plurality of spectral sub-bands,
at least a second phase modulator configured to enable modification of each of the second plurality of spectral sub-bands to decrypt the information previously encrypted by at least one of (i) imparting a phase shift to each sub-band, (ii) imparting a time delay to each sub-band, and (iii) imparting a frequency shift to each sub-band, the second optical tapped delay line being configured to enable combining the modified second plurality of spectral sub-bands into a combined optical signal.
10. The system of claim 9 comprising:
at least a third optical tapped delay line configured to enable division of each of the first plurality of spectral sub-bands into a plurality of finer spectral sub-bands, and wherein at least the first phase modulator is configured to enable modification of each of the plurality of finer spectral sub-bands to encrypt the information contained in the optical signal.
11. The system of claim 9 wherein at least one of the first and second phase modulator comprises a reflective phase modulating array.
12. The system of claim 9 wherein at least one of the first and second phase modulator comprises a transmissive phase modulating array.
13. The system of claim 9 comprising at least one computer for controlling at least one of modification of the first plurality of spectral sub-bands by the first phase modulator and modification of the second plurality of spectral sub-bands by the second phase modulator.
14. The system of claim 9 wherein at least one of the first and second phase modulator comprises at least one of a liquid crystal array, a micro-electromechanical systems device, an array of III-V or II-VI semiconductor devices.
15. The system of claim 9 wherein
at least a first pair of optical tapped delay lines configured to enable division of the optical signal into a first plurality of spectral sub-bands,
at least a second pair of optical tapped delay lines configured to enable division of the combined optical signal into a second plurality of spectral sub-bands,
wherein at least one of the first and second phase modulator comprises a transmissive phase modulating array.