Monitoring of connections

The basic cell of cable management system is the port monitor group presented at the left picture. The group consists of an infra-red (IR) reflective sensor and the part of stripline antenna (as the conductor of printed circuit board) containing the modulator of the RFID tag return signal. The modulator is based on PIN diode. In case the PIN-diode is closed the RFID reader signal passes through the lower part of the stripline antenna. When the RJ45 plug of patch cable with a near-field RFID tag shown at the same picture are inserted into the port of patch panel the IR sensor detect a connection event. At the same time ID of the the RFID tag can be detected by the RFID reader because it is very close to the lower part of the stripline antenna. If the PIN-diode is open than RFID reader signal passes trough the upper part of the antenna. Thus Received Signal Strength Indicator (RSSI) of the RFID tag is reduced considerably up to impossibility to read the RFID tag.

The main scheme of the connections monitoring subsystem located at the right picture. The controller containing the RFID reader interrogates the IR-sensors using the RS485 data bus. As a patch cable is inserted into a port of the panels the respective IR sensor changes its state immediately. The controller using the RS485 bus connects the stripline antenna of the respective panel to the RFID reader through the distributed multiplexer and the RF switch. Then the controller gets all available RFID tags near the panel by the use of RFID reader. Obviously the new RFID tag in the set of available RFID tags belong to the plug inserted just now. The port where the plug is inserted has been determined by the controller when the state of the IR sensor had been changed.

If a patch cable is disconnected from a patch panel port the controller removes respective RFID tag from the saved list of RFID tags of the patch panel and marks the port as free. It is not need to use the RFID reader in this case.

So we can clear define that a specifics plug of patch cable is inserted into a specific port of patch panel. However the described method of cable connections monitoring has significant disadvantage. If connection take place when the system lose electrical power it is difficult to recover the scheme of connections changes. In order to solve this problem we use said modulators with PIN-diode. Altering in consecutive order the state of modulators of every connected port and watching RSSI of respective RFID tag the picture of connections can be restored.