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Phase sensitive amplification in a periodically poled silica fiber

Phase sensitive amplification in a periodically poled silica fiber
Phase sensitive amplification in a periodically poled silica fiber

When a signal propagates through a transmission line, it is deteriorated by amplitude and phase noise, which reduces its signal-to-noise ratio (SNR) [1]. According to Shannon's theory, the SNR determines the maximum spectral efficiency. It is therefore necessary to limit the noise [3]. For this purpose, one can use phase sensitive amplifiers (PSA) instead of phase insensitive amplifiers (PIA) like Erbium-doped fiber amplifiers. PSAs amplify only one phase quadrature of the signal while deamplifying the other, thanks to a required phase relationship between the pump and the signal. This unique property, known as phase-squeezing, allows to obtain noise figures (NF) as low as 0 dB whereas PIAs, based on stimulated emission, cannot be go below the 3 dB quantum limit [2]. Moreover, the phase-squeezing property of PSAs can be used for quantum communication or even in metrology [1]. PSA can be realized with χ(2) material through degenerate parametric amplification [2]. The large spectral separation between the pump and the signal makes it very easy to filter out the pump after amplification. A ± 11 dB amplification with a sub-quantum NF and a regeneration of a DPSK signal was experimentally performed in LiNbO3 [3]. A fiber based approach would however be preferable for telecommunication purposes. PSA's based on four wave-mixing have been demonstrated, but the long length and the difficulty to separate pump from the signal [1] hinders its practical implementation. Here we present the first demonstration of a PSA based on periodically poled silica fiber (PPSF). This design has the advantage of all-fiber devices as well as simple pump filtering. The experimental set-up is depicted in Figure 1. A 20 mW CW fiber laser at 1550 nm is sent through a 99:1 coupler to be divided into a signal and a pump. The pump is modulated into 1 ns wide pulses with a repetition rate of 50 MHz. It is then amplified and frequency doubled in a PPLN crystal. The peak power of the 775 nm pump pulses reaches 10W. The pump and CW signal are then combined in a WDM and sent through a 30 cm long PPSF [4] where the signal undergoes parametric amplification. A second WDM is used to separate the pump from the amplified signal. The wave plates and the polarization controller in the pump path, allow to simultaneously control the polarization of the pump and the power in the fundamental mode of the PPSF (at 775 nm the fibre is slightly multimode). The relative phase between the pump and signal is controlled by fine tuning the frequency of the laser via a built-in piezo.

IEEE
Englebert, Nicolas
561be5b7-c483-4012-984e-d60a8b92e54f
De Lucia, Francesco
4a43cb71-dbd5-422e-bea6-ed48cde423f3
Sazio, Pier John A.
0d6200b5-9947-469a-8e97-9147da8a7158
Gorza, Simon Pierre
b77b1f33-b607-425d-becd-1432fa209b57
Leo, Francois
2b3c8344-1925-4bef-89a1-c55927614f2e
Englebert, Nicolas
561be5b7-c483-4012-984e-d60a8b92e54f
De Lucia, Francesco
4a43cb71-dbd5-422e-bea6-ed48cde423f3
Sazio, Pier John A.
0d6200b5-9947-469a-8e97-9147da8a7158
Gorza, Simon Pierre
b77b1f33-b607-425d-becd-1432fa209b57
Leo, Francois
2b3c8344-1925-4bef-89a1-c55927614f2e

Englebert, Nicolas, De Lucia, Francesco, Sazio, Pier John A., Gorza, Simon Pierre and Leo, Francois (2019) Phase sensitive amplification in a periodically poled silica fiber. In 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019. IEEE.. (doi:10.1109/CLEOE-EQEC.2019.8872346).

Record type: Conference or Workshop Item (Paper)

Abstract

When a signal propagates through a transmission line, it is deteriorated by amplitude and phase noise, which reduces its signal-to-noise ratio (SNR) [1]. According to Shannon's theory, the SNR determines the maximum spectral efficiency. It is therefore necessary to limit the noise [3]. For this purpose, one can use phase sensitive amplifiers (PSA) instead of phase insensitive amplifiers (PIA) like Erbium-doped fiber amplifiers. PSAs amplify only one phase quadrature of the signal while deamplifying the other, thanks to a required phase relationship between the pump and the signal. This unique property, known as phase-squeezing, allows to obtain noise figures (NF) as low as 0 dB whereas PIAs, based on stimulated emission, cannot be go below the 3 dB quantum limit [2]. Moreover, the phase-squeezing property of PSAs can be used for quantum communication or even in metrology [1]. PSA can be realized with χ(2) material through degenerate parametric amplification [2]. The large spectral separation between the pump and the signal makes it very easy to filter out the pump after amplification. A ± 11 dB amplification with a sub-quantum NF and a regeneration of a DPSK signal was experimentally performed in LiNbO3 [3]. A fiber based approach would however be preferable for telecommunication purposes. PSA's based on four wave-mixing have been demonstrated, but the long length and the difficulty to separate pump from the signal [1] hinders its practical implementation. Here we present the first demonstration of a PSA based on periodically poled silica fiber (PPSF). This design has the advantage of all-fiber devices as well as simple pump filtering. The experimental set-up is depicted in Figure 1. A 20 mW CW fiber laser at 1550 nm is sent through a 99:1 coupler to be divided into a signal and a pump. The pump is modulated into 1 ns wide pulses with a repetition rate of 50 MHz. It is then amplified and frequency doubled in a PPLN crystal. The peak power of the 775 nm pump pulses reaches 10W. The pump and CW signal are then combined in a WDM and sent through a 30 cm long PPSF [4] where the signal undergoes parametric amplification. A second WDM is used to separate the pump from the amplified signal. The wave plates and the polarization controller in the pump path, allow to simultaneously control the polarization of the pump and the power in the fundamental mode of the PPSF (at 775 nm the fibre is slightly multimode). The relative phase between the pump and signal is controlled by fine tuning the frequency of the laser via a built-in piezo.

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More information

Published date: 1 June 2019
Venue - Dates: 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2019, ICM – International Congress Centre, Munich, Germany, 2019-06-23 - 2019-06-27

Identifiers

Local EPrints ID: 438396
URI: http://eprints.soton.ac.uk/id/eprint/438396
PURE UUID: cb975e3b-97ef-45fc-9eba-a506b86f2407
ORCID for Pier John A. Sazio: ORCID iD orcid.org/0000-0002-6506-9266

Catalogue record

Date deposited: 09 Mar 2020 17:31
Last modified: 17 Mar 2024 02:55

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Contributors

Author: Nicolas Englebert
Author: Simon Pierre Gorza
Author: Francois Leo

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