Free-space optical delay interferometer with tunable delay and phase

Abstract

A free-space optical delay interferometer (DI) featuring a continuously tunable time delay, polarization insensitive operation with high extinction ratios and accurate phase and time delay monitoring scheme is reported. The polarization dependence is actively mitigated by adjusting a birefringent liquid-crystal device. The DI has been tested for reception of D(m)PSK signals. ©2011 Optical Society of America

A Survey of Optical Carrier Generation Techniques for Terabit Capacity Elastic Optical Networks

“…Gain competition and crosstalk also affects the flatness of the comb. Authors in [178], [179], [180], [181] provided a comprehensive theoretical and experimental analysis of RFS comb quality and stability in the presence of modulator and amplifier nonlinearities and investigated underlying factors for crosstalk. If the electric field of the input seed is denoted as E in (t) = E exp( j2π f 0 t), the RF drive voltages as f I = V pp sin(2π f m t) and f Q = V pp cos(2π f m t), the normalized transfer function of the RFS loop is given by [179]:…”

“…Considering the BPF in the loop blocks any frequency less than or equal to f 0 and higher than f N , the output of the RFS comb can be expressed as [179], [180]:…”

“…The noise from amplifier and crosstalk are limiting factor for effective OSNR. The resultant effective OSNR from OA and the crosstalk components is given by [178], [179] :…”

“…Sum Frequency Generation (SFG): SFG effect combines two photons at λ P and λ S to generate a third photon at λ SFG , where : [192], [195] 4 Comb enabled Terabit transmission [72], [181], [195], [196] 5 RFS Comb Stability and quality [178], [183], [191] 6 Crosstalk [179], [182] 7 Flatness [180], [183], [194] 8 Phase noise [184] 9 TNR and lines [185], [186], [187], [188], [190], [189] 10 Multi-frequency shifting [186], [187] 11 Dual loops [188], [193], [194] 12 complexity and cost [193], [194] 13 Noise Suppression [189], [190] From energy conservation perspective, one photon at frequency f P and one photon at frequency f S are annihilated by two photon absorption and the atom jumps to higher (virtual) energy level. Subsequently, a photon at f SFG = f P + f S is generated and the atom drops back to original state [199].…”

“…These filters generally exhibit a relatively poor finesse and can also suffer from relatively high insertion loss. Another commonly used comb filter is based on the Mach-Zehnder (MZ) interferometer configuration [179]. Incoming light is split in two ways and recombined after a short distance.…”