Speaker
Description
Summary
The upgrade to the existing Large Hadron Collider in CERN (European
Organization for Nuclear Research) will require a boost of speed from the
digital transceivers (4.8 Gbits/s) to allow for the increase of data output from
the particle detectors. Low power consumption and low mass will be
determinant for the performance of the detector.
By operating the laser device with no bias-current (0 current at the logic 0
stage) significant power saving can be made (in the order of 25 to 50%)
regarding its operation with an optimum bias current. Nevertheless there will
be a penalty in the eye diagram shape and therefore in the BER (Bit Error
Rate). This is because of the turn-on delay increased jitter (about 50 pico
seconds in the obtained simulation results) due to bit-pattern dependent
effects and spontaneous emission.
Since the laser will only output optical power during the logic 1 stage, no
clutter noise due to the residual optical output power at the logic 0 stage will
be present in the network, possibly simplifying a passive optical network
receiver architecture.
By using a laser model ([1]), the bellow threshold and bias-free operation of a
VCSEL (Vertical Cavity Emitting Laser) device can be determined, the BER
penalty estimated and the trade off correctly considered ([2],[3]). The data
transmission speed limit can also be determined and its operation optimized
by changing the Ioff / Ithreshold and Ion / Ithreshold ratios.
Operating a laser device in a bias-free mode can save power, lower
transceiver complexity, mass and increase system reliability ([4]).
References
[1] Silva, S., Salgado, H., “VCSEL Laser Characterization and Modelling for future Optical
Transceiver at the Super Large Hadron Collider”, Proceedings of the ICTON2009,
Conference, Azores, Portugal, July 2009.
[2] Zei, L.; Petermann, K.; Jager, R.; Ebeling, K.J., "Operation range of VCSEL-interconnect
links with “below-threshold”-biasing", IEEE 12th Annual Meeting of the Lasers and
Electro-Optics Society 1999 (LEOS '99) , vol. 2, pp. 762-763, vol. 2, 1999.
[3] Cutrer, D.M.; Lau, K.Y., "Ultralow power optical interconnect with zero-biased, ultralow
threshold laser-how low a threshold is low enough?", IEEE Photonics Technology Letters,
vol.7, no.1, pp.4-6, January, 1995.
[4] Ly Khadijetou S.; Rissons A.; Gambardella E.; Bajon D.; Mollier J-C., “Modeling and
characterization of VCSEL-based Avionics Full Duplex Ethernet (AFDX) gigabit links”,
Proceedings of the Vertical-cavity surface-emitting lasers Conference, No 12, San Jose
CA , vol. 6908, pp. 69080J.1-69080J.9, 2008.
