Engineers making fiber optic connections inside vacuum systems often reach out for off-the-shelf bulkhead connectors. While these connectors seem the best at breaching chamber walls, they increase the overall installation cost, pose mechanical design constraints, and lead to electrical problems. Often, sparks are emitted from the connectors, which can generate up to 3,000 volts of electricity. As such, many engineers are now opting for fiber optic seals made of wire feedthroughs. They allow all of the conductors in the wire harness to pass through the chamber wall with little or no pressure loss and improve electrical performance by reducing resistance and voltage drop issues that affect regular connectors. Hermetic electrical feedthroughs are particularly better, as they reduce the installation cost as well. Here are more reasons wire feedthroughs make sense.
What Are Fiber Optic Feedthroughs?
Wire feedthroughs provide an interface between UHV technology and fiber optics. They facilitate the installation of fiber optic cables in vacuum applications that need connections from the interior of a vacuum system to external equipment. Often, glass-to-glass fiber optic seals are preferable as they have a low melting point and are hence suitable for sealing various combinations of glasses, metals, and glass type ceramics.
Note that the use of feedthrough connectors depends on the application. When looking for connectors to use in systems that need a quick connect or disconnect, then bulkhead electrical connectors are befitting. Be sure to choose the best quality connectors to avoid substandard sealing performance and electrical losses. Many feedthrough applications, however, don’t need quick connect capabilities. For example, military connections are sealed for life, and hence do not need quick disconnects. The primary concern here is the need to design robust connections that can reduce electrical losses and resist the mechanical stresses of the battlefield. Here are the benefits of feedthroughs.
While bulkhead conductors are suitable for various application requirements, they are limited when it comes to the number of connections they can handle. As such, engineers are compelled to adapt the application requirements to the connectors sometimes leading to faulty connections. By contrast, continuous wire feedthroughs have thousands of conductors allowing you to mix and match them in ways off-shelf connectors don’t.
Wire feedthroughs are more space-efficient because they can easily double the number of conductors squeezed through an opening. This density advantage allows single wire feedthroughs to take the place of multiple bulkhead conductors. What’s more, feedthroughs barely protrude from the bulkhead as connectors. As such, they provide more space for the moving parts inside and outside the chamber. These space savings make a difference when designing new high-pressure hermetic seals but existing systems can benefit too.
Even the best bulkhead electrical connector experiences significant voltage drops. A typical voltage drop for connectors is more than 1 mV per crimp across a mated pin and socket. This means if the connectors experience constant resistance, it could be as high as 100 ohms. Such a loss is more than enough to compromise the signal integrity in fiber optic connections. Also, wire feedthroughs provide mechanical advantages, as they barely wear out. For example, in non-flex applications, the lifecycle of one wire feedthrough is equal to that of a wire harness enhancing its overall performance.
The misconception that bulkhead conductors are more affordable than custom wire feedthroughs couldn’t be further from the truth. As earlier highlighted, single continuous feedthrough can replace multiple bulkhead conductors when used as fiber optic seals. The savings are a result of the reduced number of individual wire harnesses required during design, production, and assembly. Eliminating bulkhead conductors not only reduces cost but also simplifies supply chains. This is because wire feedthroughs match most applications’ requirements. Another cost factor has to do with lead times, which affect time-to-market costs for new systems. Wire feedthroughs enhance speed delivery, as they are tailored to your application’s requirements. The turnaround time for custom-engineered hermetic wire feedthroughs is a week at most compared to off-the-shelf connectors which have delivery times of ten or more weeks.
Wire feedthroughs make an excellent choice for military, power transmission, fiber optic seal connections, and aerospace applications. The cost savings, space efficiency, flexibility, and improved performance are more than enough reasons to use these connectors.