We propose the concept of an integrated coherent photonic wireless transmitter based on the simultaneous injection locking of two monolithically integrated distributed feedback (DFB) laser diodes (LDs) using an optical frequency comb (OFC). We characterize the basic operation of the transmitter and demonstrate that two injection-locked integrated DFB LDs are sufficiently stable to generate the carrier signal using a uni-traveling-carrier photodiode (UTC-PD) for a real-time error-free (bit error rate: BER < 10-11) coherent transmission with a data rate of 10 Gbit/s at a carrier frequency of 97 GHz. In the coherent wireless transmission, we compare the BER characteristics of the injection-locked transmitter with that of an actively phase-stabilized transmitter and show that the power penalty of 8-dB for the injection-locked transmitter is due to the RF spurious components, which can be reduced by integrating the OFC generator (OFCG) and LDs on the same chip. Our results suggest that the integration of the OFCG, DFB LDs, modulators, semiconductor optical amplifiers, and UTC-PD on the same chip is a promising strategy to develop a practical real-time ultrafast coherent millimeter/terahertz wave wireless transmitter.

In this paper we unveil basic properties of a code Γq for digital fingerprinting based on a projective plane of order q. We consider a situation where a coalition of malicious users generates a pirated digital content in which a binary sequence w is embedded subject to the marking assumption. Here, the size of the coalition is assumed to be less than or equal to a known constant c ≥ 2. We evaluate the number of candidates of the coalition that can also generate w subject to the marking assumption. It is shown that the number of such candidates is completely determined as a function of w for the case of c = 2. In addition, we give a sufficient condition under which all the malicious users are correctly identified from w for the case of c ≥ 3. Relationships between Γq and other existing classes of codes are discussed as well.