For noiseless binary direct-detection optical channels operating with signals of classical and non-classical properties, the limits of the performance of the information at a low power level are computed. The calculations are performed and compared using two processors, the photon counter and the time intervals receiver.
The fundamental performance limits and channel capacity of optical communications systems operating over the free-space channel will be examined using quantum detection theory. The performance of the optimum quantum receiver for on{ofi keying and optical binary phase-shift keying is flrst examined as a pure-state (no-noise) problem. The classical capacity of the binary symmetric channel for these two modulation schemes will be evaluated for the optimum quantum receiver by making use of the concept of quantum measurement states. The performance of M-ary pulse-position modulation, which requires a product state representation, will be evaluated along with the performance of certain dense signal sets. Performance comparisons with classical techniques show an improvement of over 5 dB in some cases when quantum detection is employed. As a further application of the quantum detection theory, the capacity of the binary channel with on{ofi keyed modulation and quantum detection is evaluated and shown to exceed the capacity obtained with classical photon counting.
The fundamental performance limits and channel capacity of optical commu-nications systems operating over the free-space channel will be examined using quantum detection theory. The performance of the optimum quantum receiver for on{ofi keying and optical binary phase-shift keying is flrst examined as a pure-state (no-noise) problem. The classical capacity of the binary symmetric channel for these two modulation schemes will be evaluated for the optimum quantum receiver by making use of the concept of quantum measurement states. The performance of M-ary pulse-position modulation, which requires a product state representation, will be evaluated along with the performance of certain dense signal sets. Perfor-mance comparisons with classical techniques show an improvement of over 5 dB in some cases when quantum detection is employed. As a further application of the quantum detection theory, the capacity of the binary channel with on{ofi keyed modulation and quantum detection is evaluated and shown to exceed the capacity obtained with classical photon counting. I.
The fundamental performance limits and channel capacity of optical communications systems operating over the free space channel will be examined using quantum detection theory. The performance of the optimum quantum receiver for on-off keying (OOK) and optical binary phase shift keying (BPSK) is first examined as a pure state (no noise) problem. The classical capacity of the binary symmetric channel for these two modulation schemes is then evaluated for the optimum quantum receiver by making use of the concept of quantum measurement states. The performance of M-ary pulse position modulation, which requires a product state representation, is evaluated along with the performance of certain 'dense signal sets.' Performance comparisons with classical techniques shows over 5 dB improvement in some cases when quantum detection is employed. As a further application of the quantum detection theory, the capacity of the binary channel with on-off keyed modulation and quantum detection is evaluated, and shown to exceed the capacity obtained with classical photon counting.
Recently, considerable interest has emerged in quantum states of light fields other than a classical coherent state. One example of such nonclassical quantum states is the number state which features zero uncertainty for the photon number. Because of this unique property, the number states are promising as information bearing lights in direct-detection optical communications. However, if a channel is lossy, the benefit of using the number state is lessened because random photon deletions due to dissipative effect of the channel introduce inherent uncertainty to the photon number measurement at a receiver. Therefore, even in noiseless optical channels, the lossy effect must be taken into account as an important degradation factor which limits the channel performance. In this paper we compute the capacity of lossy photon channels which utilize the number state light under a certain input constraint. For binary and ternary PAM schemes, we obtain the capacity C (Γ) which is subject to the input constraint that the average number of photons per transmitted symbol can not exceed the fixed number Γ.
We provide a summary of the classical information capacity of single-mode free-space optical communication for pure-loss channels. We compare the capacities afforded by structured transmitters and receivers to that of the ultimate communication capacity dictated by the quantum nature of light, and we draw the following conclusions. The ultimate capacity can be achieved with classical coherent states (i.e., ideal laser light), but the capacity-achieving receiver (measurement) is yet to be determined. In photon-starved pure-loss channels, binary phase modulation in combination with the optimal receiver is near-capacity achieving, and more importantly, it is superior to on-off keying with either the optimal receiver (as yet to be determined) or with a photon-counter. Heterodyne detection approaches the ultimate capacity at high mean photon numbers.