By Steve Jones at HUBER+SUHNER
The persistent demand for higher bandwidth services necessitates the deployment of even higher capacity optical transmission systems, not only in long haul networks but also in metro access networks. Different opinions exist – mainly between Europe and the U.S. – around what constitutes Metro, but for many up to 40km reach is enough.
Service providers, enterprises and content providers are used to connecting to customer sites at 1G or 10G using standard wavelength division multiplexed (WDM) solutions, whether passive or active. However, when it comes to 100G, it’s a different matter. Many are now looking for low cost options on their switch/routers 100G ports, whilst also aiming to keep the transport portion of the network as simple as possible.
100G LR4 pluggable optics have been around for some time now, with most switch/router vendors supporting this specification. The 100G LR4 optic uses four x 28Gbps WDM co-propagating signals in the 1310nm region separated by 800GHz spacing. However, standard LR4 transceivers have a limited reach of <10km and so the issue of reach extension still persists.
The reach of this transceiver is specified up to 10km. The attenuation in 1310nm range of wavelength is however higher than in the 1550nm band and therefore amplification becomes an important requirement. A normal Erbium doped fiber amplifier (EDFA) would not work as it amplifies 1550nm range of signals but blocks the 1310nm signal.
For applications beyond 10km, 100GBASE-ER4 Ethernet was proposed, which has a reach specified up to 40km. The ER4 transceivers are manufactured by using a semiconductor amplifier (SOA) at the receiver subassembly inside the transceiver to increase the power budget. Commercial ER4 transceivers are available in CFP and CFP2 form-factors, but because of the power and space limitation of smaller form-factors, a 100G ER4 transceiver is not possible and therefore not available in CFP4 or QSFP28 form-factors.
Additionally, the switches and routers have started to transition to high-density QSFP28 ports to maximize the capacity and minimize space, power dissipation and finally cost.
The limitation of an ER4 based approach is not only the transceivers, but also whether the switch/router will support the interface, without the cost of an expansive platform upgrade. This effectively makes ER4 transceivers somewhat limited in its appeal.
HUBER+SUHNER Cube Optics SOA – a metro optimized amplifier delivered in a simple plug-and-play system which is independent of transceiver form-factor – provides a unique solution without the need of complex transponding equipment to boost the incoming LR4
As depicted in the figure above, with a simple addition of the SOA, the reach of the 100G LR4 CFP can be easily extended to approximately 40km. The SOA is used as an optical pre-amplifier, meaning it is used in front of the receiver to boost the incoming weak signal. For such a scenario, external amplification of the 100G LR4 signal is an optimal solution when reach must be extended further than 10km. This would not only serve the purpose of amplification, but would also inherently enjoy the independence on the transceiver form-factor.
This sort of solution takes advantage of current business infrastructure with minimal disruption to existing services and is inherently flexible to further accommodate new equipment as per demand. The 100G LR4 SOA reach extension is a unique solution that proves to be economically viable with greater space, power and bandwidth efficiency. It remains agnostic to the form factor whether CFP, CFP2, CFP4 or QSFP28.
Applications for this can be solution include:
- Carriers to extend reach for the first 100G link to customer from their local POPs.
- Internet exchanges to link 100G customers into their neutral POP.
- Financial services to connect low latency links for their offsite back-up data centre.
- Universities to connect between different parts of a campus within a city / part of a city.
- Enterprises to connect large data streams between “local DCs”.
The transformation of current network architecture to 100G systems is inevitable and businesses should prepare themselves now with the right interconnectivity solutions. Such technology is very exciting for not only everyone involved in its development and construction, but also for all those who seek a simple, reliable and cost-effective solution to extend the reach of their networks, without expensive network upgrades.
About HUBER+SUHNER Cube Optics:
HUBER+SUHNER Cube Optics manufactures and markets miniaturized fiber-optic components, modules and systems for use in data and telecommunications (Metro Core, Access, Enterprise, CATV, 3G-Telephony, Datacomm). CUBO’s components are applied in wavelength selective sensing applications in the oil & gas market, medical applications, military, security & safety equipment. Its products range from Wavelength Division Multiplexers to Switches, highly integrated optical devices like a 4 channel ROSA to rack-mountable, carrier-grade systems. Thanks to the broad range of its products and solutions, HUBER+SUHNER Cube Optics supply OEM manufacturers as well as Network Operators.
