100G Power Measurement Challenges

On , in Client Side, Ethernet, General, OTN, by Tony Goodchild

Deploying networks using CFP transceivers presents a set of challenges that did not exist with previous generations of Ethernet. Any CFP based 100G Ethernet deployment will commonly use a WDM interface – the only exception to this is in the case of using SR10 CFPs – and this in itself is enough to require a […]

 

Troubleshooting 100G Links Using PCS Lanes

On , in Client Side, Errors & Alarms, Ethernet, General, by Tony Goodchild

Understanding the condition of the PCS lanes is crucial to troubleshooting 100G links during network deployments. At the most basic level understanding that there are errors at the PCS indicates that the root cause of the fault lies with the physical signalling and not at the MAC layer or any of the high network layers […]

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Understanding 100G OTN Error & Alarm Conditions – LOL

On , in All Posts, Client Side, Errors & Alarms, General, OTN, by Tony Goodchild

Loss Of Lane Alignment (LOL) is declared on 100G interfaces when it has not been possible to successfully recover the Logical Lane Marker (LLM) from the logical lanes and then re-assemble the OTU4 frame. During the lane recovery process the LLM will be present in a lane every 16320 bytes, when the same LLM value […]

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Understanding 100G Ethernet Error & Alarm Conditions – High BER

On , in All Posts, Client Side, Errors & Alarms, Ethernet, General, by Tony Goodchild

100G Ethernet includes a process that continually monitors the performance of  received PCS data and triggers an alarm condition in the event that an excessive error ratio is detected. When receiving data at the PCS each lane is checked for errors in the 2 bit sync header in each 66b block. A counter is maintained […]

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How does Skew impact latency measurement?

On , in All Posts, Client Side, Ethernet, General, by Tony Goodchild

Now more than ever latency is a key network quality metric, with financial institutions and other Enterprise customers demanding absolutely minimal latency from their service provider. With Skew being an inherent part of a 100G Ethernet link, field engineers starting to roll out these services commonly ask how will Skew levels affect the latency measurements […]

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Understanding 100G OTN

On , in All Posts, Client Side, General, OTN, by Tony Goodchild

OTN uses a similar multi-lane mechanism to 100G Ethernet to achieve 100G rates. The parallel interfaces are defined in an appendix of the G.709 recommendation.  The recommendation includes definitions of parallel interfaces for both 40G and 100G rates and within this a new signal was defined for parallel interfaces – the Optical Channel Transport Lane (OTL). […]

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Guard Bands – Enablers For Co-existence Of Coherent 100G Signals And Non-coherent 10G NRZ Signals

On , in All Posts, General, Line Side, by Tony Goodchild

The coherent 100G transmission systems from network equipment vendors are showing an amazing robustness and tolerance for high PMD and CD. Some are reporting a PMD tolerance of up to 100ps DGD and above, while the CD tolerance can be in the range of up to 50.000ps/nm. Therefore the ideal network for deploying such coherent […]

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Understanding Polarisation Multiplexing

On , in All Posts, General, Line Side, by Tony Goodchild

Polarisation multiplexing is commonly used in 100Gb/s line side transmission as a method to increase the bit rate over the line without increasing the transmitted symbol rate. Using polarisation controllers it is possible to generate two perpendicular polarised optical signals on the same wavelength for transmission through a single fibre. As two separate signals are […]

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Understanding Phase Modulation For 100G Transmission

On , in All Posts, General, Line Side, by Tony Goodchild

There are a number of challenges to achieving 100Gb/s optical transmission rates using the technologies that have been deployed at 10Gb/s and even 40Gb/s. Using traditional transmission technologies such as NRZ modulation on the line will result in very poor spectral efficiency and a 100G signal using NRZ would not fit into the standard 50GHz […]

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Testing The Physical Interface

On , in All Posts, Client Side, Ethernet, General, OTN, by Tony Goodchild

100G testing plans must include specific attention to the physical interface. The CFP interface is no longer a single transmitter and receiver pair that can simply be checked with simple tests such as a basic optical power measurement or receiver sensitivity measurement. Utilising multiple optical lanes simultaneously makes testing the interface more complex and also testing […]

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A New Sublayer

On , in All Posts, Client Side, Ethernet, General, by Tony Goodchild

The multi-lane architecture within 100G Ethernet that comprises the PCS Lanes, CAUI and Gearbox (depending on CFP) represent a whole new sublayer of the network that must be specifically tested. This new sublayer exists only between two directly adjacent network elements that are connected via the CFP interfaces. To support this there are a number […]

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Understanding The Difference Between The Line Side And The Client Side

On , in All Posts, Client Side, General, Line Side, by Tony Goodchild

So what exactly is the difference between the line side and client side of the network?   The client side of the network is where traffic will come on-ramp into the optical backbone. In this case the client side interface will be used to interconnect between the metro networks and the optical backbone. So why […]

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