Cambridge-based photonic component and telecoms equipment manufacturer Polatis has developed a reconfigurable 32-channel filter which it launched at the European Conference on Optical Communication (ECOC) in Amsterdam.
According to Dr Jonathan James, business development manager, the filter's prime applications are optical add-drop multiplexing, dense wave division multiplexing (DWDM), channel filtering and sub-carrier multiplexing.
The filter uses a fibre Bragg grating, and is adjusted by stretching the fibre using piezoelectric actuators which, when attached to one end of the grating, vary the strain and hence the grating pitch. Piezoelectric crystals change shape when a voltage is applied and conversely generate a voltage when mechanical pressure is applied.
By using this technique, no invasion into the optical path occurs, resulting in low insertion loss. The ability to adjust the device enables passive filters to become tunable and therefore open to a wider range of applications.
The unit offers precision tuning of 32 DWDM channels with a total insertion loss of less than 3dB. Changing the strain on the fibre by approximately 0.025% is enough to shift the reflected wavelength by 50GHz without modifying the filter's shape.
The piezoelectric actuators use the company's micro actuation sensors system (Mass). The filter is in pilot production, and Dr James believes that, when it becomes commercially available, it will offer network providers cost savings.
"This device will provide customers with cost savings through reduced component counts and development time," he said. "We are combining leading edge but established optical components and applying our actuator to them."
At ECOC, the company also explained the technology behind its mirror-less 3D micro-electromechanical systems switch which also uses Mass.
The 64X64 port fibre switching subsystem is effectively an automated patch panel. Much of the loss in 3D switch systems is due to the mirrors, so the advantage of removing the mirrors is that the loss is reduced from a few dB to just one.
The light focusing element of the switch, the collimator, is mounted on high-quality piezo-actuator elements. The Mass is used instead of mirrors to move and direct the light to the next part of the system
The system has achieved switching speeds of less than 10ms.