SOA-based power equalisation for 100 Gb/s passive optical network
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Accepted Version
Date
2023-09-04
Authors
Jamali, Fariba
Murphy, Stephen L.
Antony, Cleitus
Townsend, Paul D.
Journal Title
Journal ISSN
Volume Title
Publisher
Institute of Electrical and Electronics Engineers (IEEE)
Published Version
Abstract
In Passive Optical Networks (PONs), upstream packets arriving at an Optical Line Terminal (OLT) receiver could have up to ~20 dB dynamic range (DR) due to customer-to-OL T differential loss. The conventional approach to equalise upstream packet power variation is to use a burst-mode trans-impedance amplifier (BM- TIA) that resets its electrical gain for every packet. Research attention is currently focusing on spectrally efficient 4-level pulse amplitude modulation (PAM4) as a cost-effective approach to realise 100 Gb/s PON. However, it is challenging to implement BM- TIAs with sufficient linearity, bandwidth and dynamic range to support 50 Gbaud PAM4 transmission, the current state-of-the-art achieving a DR of 15.4 dB [1], for example. Furthermore, such links must meet the 29 dB optical power budget of legacy PON systems, which can be addressed with the use of Semiconductor Optical Amplifiers (SOAs) as a preamplifier in the OLT to increase receiver sensitivity. However, operating the SOA with a constant bias degrades high-power packets due to the gain saturation induced patterning effect. The distortions are nonlinear and hence require Digital Signal Processing (DSP) far more complex than the conventional feed-forward equaliser (FFE) to recover symbols with bit error rates (BERs) below the forward error correction (FEC) limit [2], [3]. This work demonstrates the benefits and performance of SOA-based power equalisation in an emulated 100 Gb/s PON upstream (Fig. 1(a)) in a continuous operation mode. We compare two techniques [4], [5] to vary the SOA gain according to its input power: (A) variable bias current, and (B) control light injection at a wavelength different from the signal. To the best of our knowledge, this is the first time such techniques have been applied to 100 Gb/s PAM4 for the PON application. Fig. 1 (a) Experimental setup emulating pam4 pon upstream back to back transmission using ideal transmitter and receiver to study the two soa gain control schemes a and b. The extent of gain saturation (actual gain divided by small-signal gain) for each operating point (b) and ber performance (c) versus soa input power for the three modes of soa operation: fixed soa bias with no power equalisation and the two soa gain control schemes to maintain a constant output power of −2dbm.
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Keywords
Semiconductor optical amplifiers , Stimulated emission , Optical distortion , Optical saturation , Optical receivers , Passive optical networks , Optical transmitters
Citation
Jamali, F., Murphy, S. L., Antony, C. and Townsend, P. D. (2023) 'SOA-based power equalisation for 100 Gb/s passive optical network', 2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), Munich, Germany, 26-30 June, pp. 1-1. doi: 10.1109/CLEO/Europe-EQEC57999.2023.10231954
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