Presentation on theme: "Fujitsu1 New functionalities for advanced optical interfaces (Dispersion compensation) Kazuo Yamane Photonic systems development dept."— Presentation transcript:
Fujitsu1 New functionalities for advanced optical interfaces (Dispersion compensation) Kazuo Yamane Photonic systems development dept.
Fujitsu2 Outline Chromatic dispersion effect Dispersion compensating techniques Optimization of residual dispersion or its map PMD compensation Conclusions
Fujitsu3 Signal distortion due to chromatic dispersion Spectrum broadening Difference in group velocity Wavelength Group velocity Δλ 1 Time 10 Original signal Time Transmitter output Time Receiver input Time 111 Regenerated signal Wavelength Optical spectrum Δλ Pulse broadening (Waveform distortion) Optical fiber
Fujitsu4 Waveform distortion due to fiber non-linearity Transmitter out Received waveform Low optical power High optical power High power intensity Frequency chirp Refractive index change Waveform distortion due to chromatic dispersion Optical fiber Spectrum broadening
Fujitsu5 After fiber transmission 40 Gb/s optical signal Transmitter output 25 ps Transmission fiber Positive dispersion (Negative dispersion) + Dispersion compensating fiber (DCF) After dispersion comp. Negative dispersion (Positive dispersion) Longer wavelength Slow (Fast) Shorter wavelength Fast (Slow) Longer wavelengthFast (Slow) Shorter wavelength Slow (Fast) Dispersion compensation example
Fujitsu6 Fiber#1 DC allocations and dispersion maps DC Fiber#2 Distance [km] R.D. [ps/nm] Fiber#1 DC Fiber#2 Fiber#1 DC Fiber#2 DC Distance [km] R.D. [ps/nm] Distance [km] R.D. [ps/nm] Post- comp. Pre-comp. Post- & Pre- comp
Fujitsu7 Residual dispersion and tolerance of receiver Distance [km] R.D. [ps/nm] Dispersion tolerance of receiver - + Need to consider the variation of tolerance due to characteristics of transmitter, fibre non-linear effects and dispersion map. Even if residual dispersion values are same, the received waveforms are different, affected by these parameters. Parameters affecting to the tolerance - Signal bit rate - Channel counts and spacing - Distance or number of spans - Fibre type - Fibre input power - Pre-chirping of transmitter - Modulation scheme of transmitter - DC allocation / value - R.D. [ps/nm] + 0 Penalty [dB] Longer wavelength Shorter wavelength Center wavelength Allowable penalty
Fujitsu8 CS-RZOptical duobinaryNRZRZ Optical power (dBm) Wavelength (nm) Wavelength (nm) Chromatic dispersion tolerance Fibre non-linear tolerance (Maximum input power) Spectral tolerance (Degradation due to filter narrowing) 108 GHz180 GHz165 GHz70 GHz Now evaluating transmission performance Comparison of 40Gbit/s modulation schemes
Fujitsu9 A past field experiment example BerlinDarmstadt Link for field trial -400 ps/nm +900 ps/nm E/O O/E 10Gbit/s 750km WDM field trial between Berlin and Darmstadt (Ref.: OFC/IOOC99, Technical Digest TuQ2, A. Ehrhardt, et.al.) Post-amplifier Pre-amplifier E/O O/E After optimization Before Optimization
Fujitsu10 Dispersion maps and waveforms in the trial Dispersion (ps/nm) Channel 1 Channel 2 Channel 3 Channel Distance (km) Dispersion (ps/nm) Before optimization After optimization Distance (km) Channel 1 (Before) (After)
Fujitsu11 i Provisioning 1 40 Tx #40 Tx #1 2 Tx #2 Rx #1 Rx #2 Rx #40 Automatic dispersion compensation example VDC Dispersion Monitor Dispersion Monitor DC Dispersion compensator (fixed or variable) Provisioning & Tracking Collimating lens Line-focusing lens Glass plate Focusing lens 3-Dimensional Mirror Optical circulator Variable x-axis VIPA : Virtually Imaged Phased Array VIPA variable dispersion compensator DC D C > 0 D C < 0
Fujitsu12 Dispersion compensation trend Photonic network Manage dispersion or residual dispersion (dispersion map) !! NE Transmitter / Receiver Adjust parameters including residual dispersion to optimum!!
Fujitsu13 Polarization Mode Dispersion (PMD) - Well defined, frequency independent eigenstates - Deterministic, frequency independent Differential Group Delay (DGD) - DGD scales linearity with fiber length 1st-order PMD Ideal Practical Core Cladding Cross-section of optical fiber Fast axis Slow axis Fast Slow Differential Group Delay (DGD)
Fujitsu n Mode-coupling at random locations with random strength Higher-order PMD … Frequency of occurrence Instantaneous DGD (ps) Maxwellian distribution of the instantaneous DGD PMD 3.5PMD Prob.(DGD>3.5xPMD) =10 -6 = 32 sec/year Prob.(DGD>3xPMD) = 4x10 -5 = 21 min/year -Frequency dependence of DGD -Statistically varying due to environmental fluctuations -Fiber PMD unit: ps/ km
Fujitsu15 Automatic PMD compensation PMD characteristic changes slowly due to normal environmental fluctuations (e.g. temperature) But, fast change due to e.g. fiber touching High-speed PMD compensation device & Intelligent control algorithm PMD compensation scheme in receiver Before PMD comp. After PMD comp. 40Gb/s waveforms Distortion analyzer Control algorithm PMD comp. device #3 PMD comp. device #2 PMD comp. device #1 O/E module
Fujitsu16 Conclusions In fibre optical high bit rate (such as 10G or 40G bit/s) long-haul transmission systems, dispersion compensation is one of the most important items to be considered for design. Management or optimization of residual dispersion are required for photonic networks, i.e., for fibres, repeaters and optical interfaces. PMD compensation is also required especially for 40Gbit/s or higher bit rate long-haul systems.