B. Reducing Load
With the idle components in the telecommunication ne works switched off, the next step is to reduce the load on the remaining components. This strategy will be especially important in access networks since we already pointed out it is difficult to switch off elements.
Adaptive link rate is a strategy in which different line rates are supported on a link. The lower line rates are assumed to consume less power and thus power can be saved. At the customer premises this can be used to reduce the power consumption of the home gateway. Also in different access net-work technologies this strategy is showing potential. However, mainly the higher link rates in the order of 1 -10 Gbps have significantly higher power consumption compared to lower link rates. Secondly, the algorithms for adaptive link rate use larger packet buffers. These larger buffers also require hardware that needs to be powered. In core networks it makes less sense to use adaptive link rates since the traffic shows less variation.
In core networks, a promising technique to reduce power consumption is optical bypass, which is already in use for cost reduction and router capacity offloading (Fig. 2(c)). Traffic not intended for the intermediate node remains in the optical domain and is not processed by the core router. The light path is switched, using optical add/drop multiplexers (OADMs) or optical cross connects (OXCs), from an incoming fibre link directly to the appropriate outgoing fibre link. This allows to reduce the capacity of the router and the corresponding power consumption. Optical bypass is possible on single-wavelength granularity or on waveband granularity (requiring less ports in the OXC or OADM since multiple wavelengths are switched simultaneously). Wavelength conversion can be employed to optimize fibre utilization and resolve contention. Depending on the light path utilization and network size, the power saving potential of optical bypass is up to 45% [8]