Space Division Multiplexing enables the next generation of fiber amplifiers arrays

Transcription

1 N-in-1 EDFA Application note Version 15/01/2016 Highlights Space Division Multiplexing enables the next generation of fiber amplifiers arrays Amplify up 10 singlemode ports in a single Erbium Doped Few-Modes Fiber Reduce cost, footprint and power consumption Fully compatible with the existing WDM singlemode network

2 2

3 TABLE OF CONTENTS INTRODUCTION KIAMA 10-to-1 mode selective signal and pump MUX/DMUX N-in-1 EDFA CAILabs GLOSSARY p.4 p.6 p.7 p.11 p.12 3

4 INTRODUCTION As the global bandwidth in optical metro and core transmission networks grows exponentially, the need for higher transmission capacity is vital. However, it requires a densification of the transmission lines and in-line components. In addition, the need for network flexibility (reconfigurable CDC-architectures) increases further the component density in optical networks, especially at the add-drop nodes, while equipment cost strongly grows. A large portion of these passive and active optical sub-systems are used in parallel, using the exact same hardware functions in the same location. A simple and efficient way of achieving higher component density and reducing cost simultaneously is component sharing. The erbium doped fiber amplifiers (EDFAs), used to boost or regenerate the optical signal, are critical and costly components. Indeed, EDFAs are complex and they require highly reliable and expensive components such as pump diodes. The EDFAs footprint and cost reduction is already addressed by sharing components functions in some commercial arrayed EDFA by merging mechanical enclosures, electronics and using multiplechips uncooled pumps. SM-EDFA dual-chip pump SM-EDFA Driving electronics SM-EDFA SM-EDFA dual-chip pump 4 EDFA array 4

5 Space division multiplexing allows to go further in the size and cost reduction but also power consumption as it allows to share the same erbium doped fiber and pump source for amplifying several independent channels simultaneously. S-MUX & S-DMUX HR Other components Pumps 10 - in -1 EDFA 10 SM - EDFA EDFA cost: 10x SM EDFA vs. single 10-in-1 EDFA In this document, we explain how CAILabs KIAMA 10-to-1 mode selective signal and pump multiplexer allows to build the next generation of EDFA arrays. 5

6 KIAMA 10-to-1 mode selective signal and pump MUX/DMUX CAILabs 10-to-1 mode selective signal and pump multiplexer and demultiplexer allow to selectively input and output up to 10 independent spatial channels into any multi-mode (or few-mode) active fiber. In addition the KIAMA MUX supports the spatial multiplexing of two modes at the pump wavelength. These spatially multiplexed channels have the same properties as a single mode fiber and can carry several wavelength channels in a given band (e.g. the optical telecom C-band). In this document spatial channel and channel refers to a spatially multiplexed channels and should not be understood as wavelength division multiplexed channel (WDM). Pump inputs 10 input channels FM-EDFA 10 signal modes + 2 pump modes in 1 MMF 10-to-1 transverse mode MUX/DMUX Each channel is selectively injected into a propagation mode of the active MMF and the non-degenerate modes are guided by the fiber without coupling. By using an adapted fiber, designed to lift mode group degeneracies, the guided modes do not mix and each signal mode is then used as a single transmission channel. The 10-to-1 mode selective signal and pump multiplexer is a reversible passive component which can be used as a demultiplexer to fan out the independent output modes and couple them back to single mode fibers. 6

7 N-in-1 EDFA When existing EDFA arrays share the same mechanical enclosure, pump package and driving electronics, the mode multiplexed N-in- 1 amplifier uses the same pump input and doped fiber. Further to the obvious BOM cost reduction, gain sharing allows to improve the overall amplifier power efficiency. Pump power vs, number of channels for N-in-1 EDFA and SM-EDFA Transverse mode multiplexing in a multi-mode Erbium Doped Fiber allows to amplify simultaneously all the guided modes with limited cross-talk. By this mean, the erbium doped gain media and the pump modes allow to share the amplifier gain between all the transverse signal channels. Several tailored pump modes allow to balance channels differential gain and improve the amplifier efficiency. 7

8 standard pump standard pump Driving electronics KIAMA FM-EDFA KIAMA 4-in-1 EDFA At this time, the channel to channel cross-talk remains below -20 db which is sufficiently low for booster or line-end amplification. Further improvement are planned to comply with in-line applications requirement (<-30 db). The component losses are comparable with fused WDMux (2.5 db vs. 1.2 db) and are steadily improved. One drawback of this approach is the limited gain control on each individual channel. In a SM-EDFA, this tuning is mainly done by the pumps current adjustment and in some cases a mid-stage VOA. In a FM-EDFA, the gain is the same for all the spatial channels. When a single spatial channel gain or output power control is needed, the use of input and output power controller is required. This can be achieved, for example, with the VOAs already used in the network at emitter or receiver side. Finally, the shared gain fiber architecture greatly simplifies the amplifier structure, BOM and assembly. The miniaturization of the mode multiplexers allows the N-in-1 EDFA to be more compact than the smallest equivalent arrayed amplifiers with a similar level of performances. The N-in-1 EDFA amplifier array number can be increased with a simple upgrade of the Mode Selective Multiplexers and matching doped fiber. Mode selective signal and pump multiplexers are already available with up to 10 modes. A 10 modes Erbium doped FMF is under development. 8

9 We show hereunder the first amplifier results obtained with four amplified channels in a few-mode erbium doped fiber (FM-EDF). Although the gain is lower than a single-mode EDFA it is well balanced between all the channels. The gain can be easily improved reducing the system losses (>10 db on this experimental setup). Channel LP11a LP11b LP211a LP21b Total losses (db) Back-to-back system losses including EDF Output LP11a LP11b LP21a LP21b LP11a Input LP11b LP21a LP21b Cross-talks in amplification regime (Ppump = 280mW, Pin = -20 dbm) LP11a LP11b LP21a LP21b Psignal out (dbm) SNR full band (db) XT ratio of total noise 24% 19% 8% 17% Net Gain (db) in-1 EDFA performances (Ppump = 280mW, Pin = -20dBm) 9

10 FM-EDF optical microscope picture by PhLAM and IRCICA laboratories (Villeneuved Ascq, France) Ellipticity dependence of the effective index of the modes used to determine the Elliptical-Core FM-EDF target 10

11 CAILabs CAILabs is a leading provider of light shaping components. We develop and manufacture a large range of products based on our patented, efficient, and flexible technology of Multi-Plane Light Conversion. We develop and manufacture spatial multiplexers for telecommunication networks, LAN network upgrade, and multibeam shapers and combiners for industrial laser shaping and fiber amplifiers. 11

12 GLOSSARY EDFA: Erbium Doped Fiber Amplifier MUX: MUltipleXer DMUX: DeMUltipleXer CDC: Contentionless Directionless Colorless CDCG: Contentionless Directionless Colorless Gridless ROADM: Reconfigurable Optical Add Drop Multipler SM-EDFA: Single Mode Erbium Doped Fiber Amplifier FM-EDFA: Few Mode Erbium Doped Fiber Amplifier MMF: Multi-Mode Fibre FMF: Few-Mode Fiber FM-EDF: Few-Mode Erbium Doped Fiber BOM: Bill Of Material VOA: Variable Optical Attenuator 12

13 13

14 CAILabs 8 rue du 7 ème d Artillerie RENNES FRANCE