Short Courses

Digital signal processing (DSP) has always been an intrinsic component of optical communications, albeit for simple modulation techniques, framing and coding. The development of high-speed ADCs and DACs, and the increase in data processing power of CMOS ICs has enabled the implementation of complex signal processing techniques for signal modulation and demodulation. Combined with revived interest in coherent detection, algorithms have been implemented to increase the channel capacity and compensate for network impairments such as chromatic dispersion and PMD.

This course gives a basic introduction to coherent transceivers and takes a more in-depth view of the DSP building blocks and their implementation in a high-speed ASIC. The course will outline the ASIC development cycle and the steps required to transfer ideas into silicon.

Parallel filter structures in the time and frequency domain will be identified and compared. The constituent sub-blocks, such as signal shaping and CD compensation filters, polarisation compensation filters, frequency, carrier and clock recovery will be analysed. Complexity and implementation trade-offs will be discussed, along with their relative importance for different field applications.

Since the coherent receiver must compensate for the optical channel, estimation of parameters such as CD and PMD can be performed. Channel parameter estimation methods will be explained.

The course will describe methods for performing non-linear compensation, their effectiveness and relative complexity.

Next generation coherent transceivers must be cost-effective, flexible, spectrally efficient and highly tolerant to impairments in the channel. This course explains the enabling technology, practical design aspects and future research.

This course should enable you to:

• Describe the principle building blocks in a coherent optical transceiver.
• Outline the main steps for ASIC development.
• Explain the function of frequency and time-domain filters and their advantages and disadvantages.
• Explain the implementation of pulse shaping and CD filters.
• Describe techniques for frequency and carrier phase estimation
• Summarize the importance of clock recovery and describe clock recovery methods.
• Describe the components of polarization tracking filters.
• Explain how channel parameter estimation may be performed in coherent transceivers.
• Quantify the effectiveness and complexity of non-linear compensation.

This course is intended for individuals having an intermediate knowledge of digital lightwave transmission systems. It will be of value for industrial professionals (system designers, managers) who need to understand the different components in digital coherent transceivers, as well as for researchers who are new to the field.

Chris Fludger is head of DSP development at Infinera in Germany, where he specializes in System Design and Digital Signal Processing for flexible communications. Previously, he has worked on the development of several generations of coherent optical transceivers at Cisco and CoreOptics. He has received Master's and Doctorate degrees in electronic engineering from Cambridge University, UK. At Nortel Networks his focus was electronic signal processing, advanced modulation techniques and Raman amplification.