As the traffic demand continues growing, telecom network providers have planned introducing the newly developed coherent 100G transport software in their networks to satisfy the demand. History shows us that network service providers have made use of every stage of the new channel capacity available from equipment developers.
The figure below shows the timeline for increases in fiber link capacity operating provider’s networks. In early 1990s, a capacity of a few hundred Mbps per link and just on channel per strand of fiber inside a transport network was typical. As email was a new communication tool in the centre 1990s, the fiber capacity gradually increased to a couple Gbps, and this growth continued to deal with the demand that individuals needed to start accessing the web. Into the later 1990s, fiber capacity grew even larger with the deployment of 10 Gbps channels and WDM techniques to multiplex and amplify a small number of wavelengths (4-8) on a single fiber pair. In early 2000s, Internet usage became commonplace but networking kept pace using the introduction of DWDM techniques that could support 40, 80, or maybe more wavelengths allowing fiber capacities to be near Tbps. For MUX/DeMUX solutions with different DWDM wavelengths, please visit Fiberstore. This extensive fiber capacity increase helped the transport network support continually increasing user demands. In the late 2000s, the introduction of 40G channels gave the capability of the networks another boost. By 2010, video sharing on the web by applications such as YouTube along with other video when needed (VoD) services started to stress existing network capacity. The development of the fiber capacity to approximately 10 Tbps per fiber. This will address near term capacity requirements, but moving forward, cloud computing along with other bandwidth hungry applications will continue to consume network resources, and new optical techniques to increase channel capacity and optical link capacity is going to be introduced progressively.
The coherent 100G PM-QPSK system selected by the industry is able to run at the same channel spacing (50 GHz) like a 10G commercial system does in existing networks, and so the 100G system can offer enough capacity for network service providers to support customer demands in the near term without a network overbuild. Using the new 100G system, service providers expect the cost per bit declines in the same rate as or perhaps a faster pace than the decline rate of serves prices service providers can charge their clients, so that providers are able to remain competitive.
Before telecom service providers introduce commercial coherent 100G software in their networks, normally a series of technology trials must be conducted in their existing networks to determine the performance of the new technology. The primary purpose of the technology trials would be to guarantee the 100G channel behaves well in existing fiber network infrastructures. Fiber routes within the field may have high transmission attenuation, high PMD values, multiple connections and splicing points, various fiber types, etc. While most lab experiments are conducted with fiber loop configurations, a linear configuration in field trials is much more preferred to mimic optical links in tangible networks. Field trials give network providers proper expectation for that performance of the systems, which will be installed in networks. Issues present in these trials may also be sent back somewhere developers for further product improvement. In a single field trial a 112 Gbps coherent channel transmitted over 1730 km deployed DWDM link in a service provider’s network, while using DWDM Multiplexer. A carrier suppressed RZ and differential PM-QPSK modulation format was utilized for the channel in the trial. The trial results show that the coherent 100G channel has the capacity to serve long term routes. The plug and play performance of the equipment and robustness to chromatic dispersion and PMD impairments was demonstrated in the trial. Co-propagating the 100G channel with adjacent 10 Gbps signals without touching the fiber infrastructure proved one viable migration road to next generation networks. It’s a requirement for service providers to maintain the networks scalable and cost-effective while increasing channel capacity and fiber ability to have next-gen multi-terabit networks.
In another field trial a real-time, single carrier, coherent 100G PM-QPSK upgrade of the existing 10G/40G terrestrial system was demonstrated inside a service provider’s network. The field experiment shows the performance of the 100G channel sufficient for error-free operation after FEC over installed 900 km and 1800 km fiber links. The experiment proves that flexible and seamless 100 Gps channel upgrades to existing 10G and 40G DWDM systems are possible and practical.
Yet another coherent 100G channel field trial was performed on dispersion shifted fiber (DSF) links. The trial involved eighty 127 Gbps channels propagating on a deployed fiber link. L-band specturn was used to avoid zero dispersion reason for specturn, differnet from using C-band for SMF or NZDSF for additional common cases. The 100G channels, with 50 GHz channel spacing, traveled over 458 km DSF successfully with L-band EDFA only. Sufficient Q-margins remained as left for the 80 channels following the 458 km transmission. This field trial demonstrated that a 10 Tbps calss capacity DWDM product is feasible underneath the condition of small local dispersion by deploying coherent detection and high overhead (20%) coding gain FEC. This trial represented the highest fiber capacity in the field at the time the trial was conducted.
The reason for introducing 100G channels into transport networks is to carry large IP data traffic across IP networks, therefore, an “end-to-end” transport trial, i.e. an entire data transport trial from data equipment to data equipment, using a coherent 100G channel transmission over a long distance, is particularly meaningful to service providers. One such field trial, which involved a worldwide network company, a data equipment developer, a transport equipment developer, and a client interface developer, continues to be reported. In this trial a 112 Gbps single carrier real-time coherent PM-QPSK channel from a transponder carried native IP packet traffic over 1520 km field deployed fiber, with 100GbE router cards and 100G CFP interfaces. This trial shows the feasibility of interoperability between multi-suppliers’ equipment for 100G transport. This field trial, which fully emulated an operating near-term deployment scenario, confirmed that all key components required for deployment of 100GbE technology are maturing at the time the trial was conducted (early 2010).
The detailed configuration of the trial is shown in the figure. A 10GbE test set generates 10GbE traffic for Router 1 and also the test set can be used for analyzing packet throughput too. Another router (Router 2) is used to accept a GbE signal containing a video signal using a video encoder and to send the recording signal to some video display via a video decoder following the signal transverses the trial path. Router 2 connects to Router 1 with another 10GbE link, containing the video traffic. Router 1 routes both 10GbE data streams to one of the 100GbE cards and routes back the 10GbE data streams form the other 100GbE card towards the corresponding 10GbE ports. The 100G CFP interfaces are used to connect 100GbE cards and the 100G transponder. The transmitter port of the CFP in the first 100GbE card is connected to the receiver port of the CFP in the transponder and also the receiver port of the second 100GbE card is linked to yhe transmitter port from the CFP in the transponder. The receiver port from the CFP in the first 100GbE card and also the transmitter port of the CFP in the second 100GbE card are of a fiber jumper (fiber patch cable) to shut the loop. The CFP transponder sends the 112 Gbps signal towards the fiber route-equipped having a long haul DWDM system. Both directions of the inline amplifiers have been used for the trial to save on equipment needed.
With these successful 100G system field trials, telecom network providers and other network operators have been convinced that the only optical carrier PM-QPSK with coherent detections is easily the most promising 100G channel solutions, at least for the time being. Now commercial 100G systems are for sale to the customers of the equipment developers and the customers are likely to enjoy the ten times fiber capacity begin their networks.
