Traditionally, products have gone down the path of modularity for two reasons: cost and/or ease of replacement without effecting existing services.  When the LGX form factor was first created for optical splitters, it made sense to have a modular approach for the first reason and to a lesser extent, the latter reason.  When optical splitter modules were first put into the LGX form factor, the cost per splitter was considerably higher than it is today. Therefore, inserting modules into a chassis became a cost effective way to “grow” as needed.  At the same time, the quality of those modules was not as high nor as repeatable as it is today, so despite any changes being service effecting (passive elements are not capable of protection switching around an outage) having the ability to replace the modules was also a key advantage.

In recent years, companies have shown the benefits of “copying” and sending traffic from network backbones to purpose-built monitoring devices…no interference with the existing, “live” traffic and the traffic can be analyzed in real-time or stored for later playback. However, the best approaches to “copying” and sending the traffic to be monitored has been a source of contention.  As 40/100G becomes more prevalent, how the traffic is accessed will become increasingly important.

Initially, the Switched Port Analyzer (SPAN) ports were used to deliver copies of traffic to analyzers, but this has posed several problems at the 1G and 10G data rates, which likely will increase exponentially with 40/100G:

• SPAN ports are part of the switch/router and operate in much the same way as typical ports, so the data is not always an exact copy
   
• Traffic congestion both on the router and on the SPAN port itself can result in increased latency or the traffic to be dropped completely
   
• Relying on a device that could be creating the problem to help identify it can be a self-defeating exercise
   

As virtualization and cloud applications become more and more prevalent in Data Centers, POPs, Head-ends, and Central Offices, the available rack space needed to house the equipment for these applications is shrinking.  While the space needed to store, process, route, or switch the data becomes more compact, one thing that remains difficult to reduce is the physical layer infrastructure. As traffic enters or exits a facility, most providers want the capability to monitor what is being delivered or sent to/from their site. At the larger sites, this data traffic is riding on fiber, and in many cases, there are a number of fibers coming into or out of a given site. To be able to accurately monitor this traffic, a passive optical tap is used to duplicate the traffic and send it to a monitoring device that can analyze the header information native to the traffic type.  In the past, these optical taps were relatively expensive and bulky. Even today, most vendors cannot provide more than 24 taps in a single 1RU footprint.