Loudon, R and Jedrkiewicz, O and Barnett, S M and Jeffers, J (2003) Quantum limits on noise in dual input-output linear optical amplifiers and attenuators. Physical Review A, 67 (3). -. ISSN 1094-1622Full text not available in this repository. (Request a copy from the Strathclyde author)
The input-output relations for linear amplifiers and attenuators that have two input and two output channels are used to derive inequalities that relate their gain profiles and output noise spectra. The results generalize earlier derivations, which mainly focus their attention on single-channel devices, to the two-ended amplifiers and attenuators often used in practical communications systems. The present inequalities are satisfied by the results of previous calculations for specific model systems. It is shown that; in contrast to single-channel devices, a two-ended system can act as an amplifier for some input signals and an attenuator for others, even when all the signal frequencies are the same. The output from the two-channel amplifier has a minimum noise determined by the sum of the gains for both input channels, even when only one input channel is used and the other is in its vacuum state. The conditions on device construction needed to achieve equal gains for signals that arrive at the two ends of the device are determined. The present results reduce to those of single-channel theory in special cases where the two output channels are each separately fed by only one of the two input channels.
|Keywords:||electromagnetic fields, commutation relations, 4-port devices, dielectrics, Optics. Light, Atomic and Molecular Physics, and Optics|
|Subjects:||Science > Physics > Optics. Light|
|Department:||Faculty of Science > Physics|
|Depositing user:||Pure Administrator|
|Date Deposited:||17 Jun 2011 11:13|
|Last modified:||04 May 2016 18:22|