BLong et all, good article on what HLIT is doing,channel reuse,optically add/dropping selected wavelengths, managing the integrity of the system.
telecoms-mag.com
The European situation was slightly different. There, the average operator is not faced with the fibre-based limitations, but does have to cope with variances between the planned and actual customer take-up of services. Where take-up has been considerably greater than forecast, operators have found themselves up against immediate capacity-related issues on newly-installed network bases -- not an enviable situation.
However, once a series of viable solutions became available to solve capacity-based limitations, a new issue came to the fore: connectivity. A catalyst for this came from metropolitan network operators -- WDM technologies appeared to offer a viable means of accessing a limited number of channels at different locations, through a point-to-point system. The advent of the necessary component technologies -- principally improvements in optical filter techniques and network management which were introduced during 1997 -- gave network infrastructure owners a significant new option. Hardware costs could be reduced, allowing partial access to the optical spectrum. This removed the expense of having to install back-to-back WDM line systems, based on previous requirements to access and process the whole spectrum.
The ability to access optical channels at intermediate stages economically represented an important breakthrough. The stage was then set to apply the same technology into ring-based applications, in order to address network configurability requirements -- the next focal point. In this case, there is a greater need to be able to re-use optical wavelengths. Once again, application was dependent on the availability of the required optical component technologies -- with the first introductions being launched last year, addressing the issue of optical channels and the management of re-circulating noise.
This focus on ring applications paved the way for the development of a fully-fledged optical add/drop terminal, which could handle a number of needs, such as:
the ability to manage the optical channels remotely and locally;
a reduction of the optical amplifiers in cascade, in order to minimise the optical noise-based impairments on the systems;
the need to reduce the optical signal penalty for wavelengths not being dropped;
the ability to add and drop signals in any order.
In addition to highly reliable pre-tuned lasers, an optical switch was needed. There was also a requirement to manage fibre paths within terminal equipment, to maintain signal integrity. The overall challenge was to provide a mechanical equipment structure, readily accessible by the operator.
This represents the current stage of development -- further advances in optical switch component technology have paved the way for commercially-available optical add/drop terminals this year, representing the latest milestone towards achieving a full photonic network infrastructure. The next concern is the need to achieve remote management of the installed terminal.
However, challenges continue to present themselves. These include the need to maintain end-to-end integrity of an optical channel, enabling a new generation of manageability applications to be produced. Also, as the implementation of WDM technologies continues to evolve towards the end user, the need for interconnections between rings and small islands of the networks will gain increasing importance. The resulting higher capacity optical cross connect technology will be instrumental in addressing the need for future network salability -- an essential aspect of progress.
Significant milestones have already been achieved towards the realisation of completely photonic networks. The development of erbium-doped fibre amplifier technology represents a significant breakthrough, enabling WDM signals to be regenerated in bulk, thereby reducing costs dramatically
Well HLIT is gonna be there first with an All Optical Cable Network. Its going to be opaquely add/dropped with signal regeneration.
Tim |
