Technology - Infrastructure - Long Distance 2 - Fibre, Modulation, Amplification and 40Gbs

Synopsis

This report discusses lasers, modulation techniques and the two major optical amplification techniques: and distributed Raman and Erbium Doped Fibre Amplifiers (EDFAs). Also discussed are the prospects for soliton transmission in WDM systems and the challenges 40Gb/s long-haul fibre links and how they can be overcome with Forward Error Correction (FEC) and a variety of sophisticated modulation techniques.

Table of Contents

• 1. Synopsis
• 2. Lasers, modulation and detectors
  • 2.1 Stable, tunable, lasers
    • 2.1.1 Tuning by temperature and current
    • 2.1.2 Novel tuneable laser techniques
    • 2.1.3 Standards for tuneable lasers
  • 2.2 Modulation
    • 2.2.1 LiNO Mach-Zendher modulators
  • 2.3 Wavelengths and multiplexing
  • 2.4 Optical amplification
    • 2.4.1 Stimulated emission from energised atoms
    • 2.4.2 Semiconductor Optical Amplifiers (SOAs)
    • 2.4.3 EDFAs
    • 2.4.4 Raman distributed amplification
    • 2.4.5 Benefits of Raman amplification
    • 2.4.6 Limitations of Raman amplification
    • 2.4.7 Long single-link distances
    • 2.4.8 Safety and fibre damage
• 3. 40Gb/s
  • 3.1 Optical Signal to Noise Ratio (OSNR)
    • 3.1.1 The eye pattern
  • 3.2 Forward Error Correction (FEC)
  • 3.3 Modulation techniques
    • 3.3.1 Non Return to Zero (NRZ)
    • 3.3.2 Return to Zero (RZ)
    • 3.3.3 Chirped Return to Zero (CRZ)
    • 3.3.4 Duo-binary
  • 3.4 Differential Phase Modulation Keying (DPSK)
  • 3.5 Differential Quaternary Phase Shift Keying (DQPSK)
  • 3.6 40Gb/s fibre links
    • 3.6.1 Correcting chromatic dispersion
    • 3.6.2 Slow progress towards 40Gb/s
    • 3.6.3 10Gb/s with duo-binary may be optimal
• 4. Soliton transmission
  • 4.1 Barriers to practical use of solitons
    • 4.1.1 Precise control of signal level
    • 4.1.2 Precise control of fibre dispersion
    • 4.1.3 Crosstalk between solitons
    • 4.1.4 Polarisation mode dispersion
• 5. Related reports