Calvin Chun-Kit Chan

Dynamic resource allocation for all-optical multicast based on sub-tree scheme in elastic optical networks

All-optical multicasting with a single light-tree suffers inefficient distance-adaptive spectrum allocation from its large tree-spanning size. We propose a routing modulation format and spectrum allocation (RMSA) algorithm based on sub-tree scheme to improve spectrum utilization.

Non-orthogonal multiple access with phase pre-distortion in visible light communication.

Non-orthogonal multiple access (NOMA) offers a good balance between throughput and fairness for visible light communication (VLC). This work presents a phase pre-distortion method to improve the symbol error rate performance of NOMA uplink with successive interference cancellation (SIC) decoding in VLC. Both theoretical analysis and experimental evaluation have shown that the proposed phase pre-distortion method improves the bit-error-rate (BER) performance for NOMA under both low and high relative power ratios. Specifically, at low relative power ratios, the proposed method can eliminate the possible BER floors and alleviate the power ratio requirement by 2 dB at the BER of 3.8 × 10-3.

Image processing based common phase estimation for coherent optical orthogonal frequency division multiplexing system

A novel common phase error estimation method based on image processing technique is proposed. Both numerical simulations and experiments prove its feasibility to compensate phase noise with improved spectral efficiency than the pilot-subcarrier aided method.

Digital domain power division multiplexing DDO-OFDM transmission with successive interference cancellation

Two independent 2.5-Gb/s DDO-OFDM signals are simultaneously transmitted over 25km SMF using digital domain power division multiplexing and successive interference cancellation. With optimized power division ratio and enhanced SD-FEC, the spectral efficiency can be doubled.

Flexible and scalable wavelength multicast of coherent optical OFDM with tolerance against pump phase-noise using reconfigurable coherent multi-carrier pumping

Recently the ever-growing demand for dynamic and high-capacity services in optical networks has resulted in new challenges that require improved network agility and flexibility in order for network resources to become more consumable and dynamic, or elastic, in response to requests from higher network layers. Flexible and scalable wavelength conversion or multicast is one of the most important technologies needed for developing agility in the physical layer. This paper will investigate how, using a reconfigurable coherent multi-carrier as a pump, the multicast scalability and the flexibility in wavelength allocation of the converted signals can be effectively improved. Moreover, the coherence in the multiple carriers prevents the phase noise transformation from the local pump to the converted signals, which is imperative for the phase-noise-sensitive multi-level single- or multi-carrier modulated signal. To verify the feasibility of the proposed scheme, we experimentally demonstrate the wavelength multicast of coherent optical orthogonal frequency division multiplexing (CO-OFDM) signals using a reconfigurable coherent multi-carrier pump, showing flexibility in wavelength allocation, scalability in multicast, and tolerance against pump phase noise. Less than 0.5 dB and 1.8 dB power penalties at a bit-error rate (BER) of 10-3 are obtained for the converted CO-OFDM-quadrature phase-shift keying (QPSK) and CO-OFDM-16-ary quadrature amplitude modulation (16QAM) signals, respectively, even when using a distributed feedback laser (DFB) as a pump source. In contrast, with a free-running pumping scheme, the phase noise from DFB pumps severely deteriorates the CO-OFDM signals, resulting in a visible error-floor at a BER of 10-2 in the converted CO-OFDM-16QAM signals.

A switching architecture for remote radio head protection in cloud radio access networks

Cloud radio access network (C-RAN) is a persuasive solution to the burst capacity in future 5G mobile system and it can tackle the tidal effect in mobile networks for better resource utilization. We propose a remote radio head (RRH) protection scheme to assure the availability of the RRHs. A protection layer is proposed to support re-configurable protection of the RRHs, with good scalability.

Simple Self-Homodyne Detection Scheme for Optical OFDM With Inserted Pilot Subframes and Application in Optical Access Networks

In this paper, a simple self-homodyne detection scheme is proposed and experimentally demonstrated for applications in optical access networks. Unmodulated pilot subframes are periodically inserted and interleaved with data subframes to form an orthogonal frequency-division multiplexing (OFDM) signal. Owing to the coherence between the embedded pilot and data subframes, a Mach–Zehnder delay interferometer with a free spectral range equal to the frequency of the subframe is deployed for the self-homodyne detection of the OFDM signal. It saves the local oscillator and optical hybrid, which are usually used in a conventional coherent receiver, thus reducing the hardware complexity and implementation cost. Meanwhile, the digital signal processing (DSP) for the self-homodyne detection is free from carrier-frequency-offset compensation and carrier-phase estimation, reducing the complexity, power consumption, and latency of the system. It also allows the use of a low-cost laser source as the source for the downstream signal. The proposed scheme provides a cost-effective and energy-efficient downstream solution for optical access networks, owing to the hardware saving and complexity reduction in DSP. A 10-Gb/s OFDM downstream transmission over a 20-km standard single-mode fiber is experimentally demonstrated with an error-free operation, using both a 10-MHz distributed feedback laser and a 100-kHz external cavity laser as downstream laser sources.

Pump-phase-noise-tolerant wavelength conversion for coherent optical OFDM using coherent DFB pumping

We experimentally demonstrate an OWC scheme for CO-OFDM using coherent DFB pumping. The tolerance against pump phase noise with coherent pumping enables the use of low-cost 2MHz-linewidth DFB as pump to realize OWC of 12Gbps QPSK-CO-OFDM with 1dB penalty.

Mitigation of inter-carrier interference induced by phase noise and residual carrier frequency offset in CO-OFDM systems

We propose and experimentally demonstrate a novel method to mitigate the inter-carrier interference (ICI) induced by laser phase noise in CO-OFDM systems. Numerical studies also show its capability of jointly mitigating phase noise and residual carrier frequency offset.

Virtual private networks in OFDM-PON supporting radio-over-fiber based on physical-layer network coding

We propose and experimentally demonstrate a VPN scheme based on physical-layer network coding in OFDM-PON that supports heterogeneous services. Two signals are coded together physically and respectively decoded at destined users. The proposed scheme improves VPN throughput compared to conventional schemes.