High-speed all-optical encryption and decryption based on two-photon absorption in semiconductor optical amplifiers

We propose a scheme to realize high-speed all-optical encryption and decryption using key-stream generators and optical XOR gates utilizing the ultrafast two-photon absorption (TPA)-induced phase change in semiconductor optical amplifiers (SOAs). The key used for encryption and decryption is a high-speed all-optical pseudorandom bit sequence which is generated by a linear feedback shift register (LFSR) together with optical XOR and AND gates. The input intensities to the SOA are high enough so that the fast TPA-induced phase change is larger than the regular induced phase change. We also designed and investigated three more secure key-stream generators, i.e., a three LFSR cascaded design generator, an alternating step generator, and a shrinking generator. Results show that this scheme can realize all-optical encryption and decryption by using key-stream generators at high speed up to 250 Gb/s.