Wavelength control in WDM-PON using pilot tones

Transcription

1 Wavelength control in WDM-PON using pilot tones Michael Eiselt, ECOC WS5: Is NG-PON2 an ultimate access solution? Is there anything coming afterwards?

2 Introduction Multiple applications of WDM-PON: DSLAM backhaul Business access Mobile backhaul Mobile fronthaul Customer Premises Equipment (CPE) Baseband Unit (BBU) Hotel 2

3 Introduction Multiple applications of WDM-PON: DSLAM backhaul Business access Mobile backhaul Mobile fronthaul Multiwavelength Head End Remote node Tail End Multiple architectures Tree Dropline Horseshoe / Ring Multiwavelength Head End Remote node Tail End Multiwavelength Head End Remote node Tail End Multiwavelength Head End 3

4 Introduction Multiple applications of WDM-PON: DSLAM backhaul Business access Mobile backhaul Mobile fronthaul Multiple architectures Tree Dropline Horseshoe / Ring Multiple standardization approaches ITU-T Q.2/SG15: NG-PON2 (G.989.x) with WDM-PON overlay ITU-T Q.6/SG15: port-agnostic interfaces (G.metro) 4

5 Introduction Multiple applications of WDM-PON: DSLAM backhaul Business access Mobile backhaul Mobile fronthaul Multiple architectures Tree Dropline Horseshoe / Ring Multiple standardization approaches ITU-T Q.2/SG15: NG-PON2 (G.989.x) with WDM-PON overlay ITU-T Q.6/SG15: port-agnostic interfaces (G.metro) One problem: Wavelength control of a remote transmitter 5

6 DeMUX MUX Cyclic AWG Example: Tree Architecture OLT Tx Array 1... N Rx Array 1... L C L-Band ~ 97.2 / 48.6 GHz C-Band 100 / 50 GHz RN ONU N C L T-LD Rx ONU1 C L T-LD Rx N Reduce cost of tunable ONU: Integration of L/C coupler, tunable laser, photo diode Reduce tunable laser componentry No wavelength locker No thermo-electric cooler (TEC) depending on laser Avoid calibration of each laser Generic tuning algorithm, parameters adapted based on current wavelength tuning feedback Network based wavelength control for all ONUs, located at OLT 6

7 Network based wavelength control OLT Tx Array... 1 Demux N L C RN... Diplexer T-SFP ONU Rx Array... 1 µc1 Mux AWG L-Band C-Band ctrl µc2 N Problem: ONU laser can tune to any wavelength, but doesn t know to which and doesn t have an internal feedback 2-step tuning of remote ONU laser: Startup: power monitoring at OLT to find correct channel Continuous wave locker monitoring to maintain accurate wavelength Startup procedure: Sweep laser over multiple channels AWG in remote node port determines correct wavelength Monitor channel power on OLT receiver array Send feedback from OLT to ONU using (pilot tone) communication channel 7

8 Automatic channel lock at start-up Target channel wavelength Laser starts around target wavelength (here: ~ 400 GHz window) Received power is communicated from OLT to ONU via tone channel Start-up tuning time ~15 seconds Limited in experiment by speed of OLT-ONU communication 8

9 Demux µc1 Mux AWG Step 2: Tuning with central wave locker OLT OM/OD ONU 1 L-Band Tx Array T-SFP N... 1 L C C-Band... 1,f 1 Tone1 µc2 Diplexer Rx Array... 1 N WL WL: Wave locker etalon reference T-SFP ToneN N,f N ONU N µc2 9 1 f 1 N f N wavelength ONUs over-modulate data signal with distinct pilot tone frequencies Optical WDM signal is received in wave locker and AM tone powers are extracted by FFT Wavelength error is calculated by comparing the etalon output power with the reference AM tone power for each tone / wavelength Received power and wavelength error are communicated to TE via downstream control communication channel (here: pilot tone)

10 Long-term wavelength control Constant laser temperature Laser temperature varies over time Laser frequency constant within ~+/- 2.5 GHz for constant temperature Mode jumps occur, when temperature is varied Constant temperature operation required to avoid outages Can be achieved e.g. using high-temperature material and heating 10

11 Conclusion Low cost tunable laser by reducing componentry (wave locker) Network based wavelength control required Feedback from head-end (OLT) via control communication channel Wavelength stability sufficient for 50 GHz channel spacing with constant temperature operation (e.g. heating) 11

12 Thank You IMPORTANT NOTICE ADVA Optical Networking is the exclusive owner or licensee of the content, material, and information in this presentation. Any reproduction, publication or reprint, in whole or in part, is strictly prohibited. The information in this presentation may not be accurate, complete or up to date, and is provided without warranties or representations of any kind, either express or implied. ADVA Optical Networking shall not be responsible for and disclaims any liability for any loss or damages, including without limitation, direct, indirect, incidental, consequential and special damages, alleged to have been caused by or in connection with using and/or relying on the information contained in this presentation. Copyright for the entire content of this presentation: ADVA Optical Networking.

13 Characterization of the laser Gain Phase MMI Reflector 1 Modulated grating Y-branch laser ( Syntune ) 3 currents for wavelength control AR Reflector 2 Reflector 1 Reflector 2 Phase Linear or quadratic fit to measurements Currents depend on temperature Typical temperature gradient for constant current: -12 GHz/degC Mode jumps for larger temperature variations Temperature ( C) Frequency setpoint f [GHz] for 25degC 13