Gamma Quadrant Relay Station

Wormholes can be used as shortcuts to cover immense distances of space.  The only stable wormhole known to Starfleet and the Federation is located near the planet Bajor, and links that sector of the Alpha Quadrant with the Gamma Quadrant.  While the wormhole makes travel between the two quadrants possible, it originally presented a problem for communications:  the wormhole only opens when a starship approaches to travel through.  Until 2371, subspace signals could not pass through when it was in its closed state.  This meant that Federation starships in the Gamma Quadrant were out of touch with the rest of Starfleet.  Even when the wormhole was open, signals that were sent through were so distorted by the electromagnetic interference that they were often unintelligible.  The Federation was desperate to find a way around this problem, as communications through the wormhole would facilitate exploration and allow Starfleet and Bajorans to monitor Dominion activity.  Deep Space Nine's Chief of Operations Miles O'Brien and Science Officer Jadzia Dax attempted to set up a subspace relay system that would operate through the wormhole, but their efforts met with little success.  This was partly because the phase variance in the transceiver coils, while less than 0.01 percent, was too high for communications signals to get through.

Despite their best efforts, O'Brien and Dax were unable to find a way around all of the problems.  The situation was only resolved a year later in 2371, when three Cardassian scientists visited DS9 to work on the project.  The Cardassian team consisted of Gilora Rejal, Ulani Belor, and Dejar, an undercover agent for the Cardassian Obsidian Order.

The Cardassian scientists planned to place one transceiver array on a signalling platform in the Idran system, 2km from the mouth of the far side of the wormhole in the Gamma Quadrant, and another in the Alpha Quadrant on Deep Space Nine. In order to accommodate the transmissions, some adjustments needed to be made to DS9's signalling array.  The Cardassians believed they could fit their transceiver inside a Federation signalling platform and use the existing power grid to send and test various types of soliton pulse that would act as a carrier wave.  This was a similar approach to the one used by O'Brien and DAx, but the Cardassians claimed that by using their transceiver they could have the phase variance that had troubled Starfleet and maintain the signal integrity.  They decided to test several types of soliton pulse to determine which would be best able to counteract the interference caused by the inside of the wormhole.

The Cardassians found that O'Brien had made many modifications to DS9's circuitry since the Federation took over.  This meant that the switching relays in Ops no longer had the same carrying capacity and were unable to handle the signal load of the transceiver.  However, after some initial difficulties the Cardassian scientists and O'Brien were eventually able to make the necessary changes.  Once the array on Deep Space Nine was ready for operation, the U.S.S. Defiant NX-74205 deployed the subspace relay platform in the Gamma Quadrant and targeted it at the wormhole.  The relay's transceiver array was activated, and the Cardassians attempted to send a carrier wave through the wormhole.  The first wave, which was initiated in a delta band frequency, was unsuccessful, so the Cardassians tried to send a theta band wave.  Unfortunately, this resulted in an immediate neutrino surge in the wormhole which caused it to open violently and increased its gravity well by a factor of three.  A passing silithium laden commet was subsequently pulled toward the wormhole.  This had potentially disastrous consequences:  if the comet containing the silithium was allowed to enter the wormhole, it would cause a cascade reaction and collapse the wormhole, sealing it permanently.  Attempts were made to destroy the comet using wide beam phasers, but these efforts were sabotaged by Dejar and merely caused the comet to shatter into three pieces.

With no way to divert the fragments, Commander Sisko was forced to pilot a shuttle in between the fragments and surround them with a subspace field to stop the silithium leaking out.  Sisko successfully navigated through the wormhole, but there was some silithium leakage.  This had the unexpected but very welcome effect of making communications through the wormhole possible.  The amount of silithium leaked was just enough to leave a subspace filament inside the wormhole that could carry communication signals like a carrier wave.