Squeezing and fiber-optic communications

We review the relations between squeezing and optical communication advances and introduce the field of distributed phase-sensitive amplification, where we expect this cross-fertilization to happen next. We consider the quantum noise properties of phase-sensitive amplifiers in lossy fiber in the case of arbitrary parametric gain distribution along the fiber length. Three most important cases of gain followed by loss, loss followed by gain, and ideally distributed gain, are discussed in detail. We show that ideally distributed phase-sensitive amplifier maximizes the signal-to-noise ratio for a fixed nonlinear phase shift in the fiber span, and is promising for both classical and quantum communications.