Fiber optic switching network

DETAILED DESCRIPTION FIG.
1 shows a ring wiring center (RWC) represented by broken block 10.
The center includes a plurality of node switches NS1, NS2, - - - , NSN.
Each node switch may be implemented as indicated below.
The node switches share a common fiber 12.
Fiber 12 is a continuous single strand which links all the switches and returns to connect to itself, tail in mouth, as indicated by arrows 13 and 14.
Each node switch operates to bypass a portion of fiber 12 by routing information through a node or terminal.
The nodes are designated RN1, RN2, - - - , RNN and TN1, TN2, - - - , TNN and would, in practice, constitute local area network (LAN) terminals.
Interconnections between a node NSi and the associated receiving and transmitting nodes RNi and TNi (where i is a dummy variable) are made by optical fibers 15.
sub.
R1, 15.
sub.
T1, 15.
sub.
R2, 15.
sub.
T2, - - - , 15.
sub.
RN, 15.
sub.
TN.
Optical fibers 15.
sub.
Ri and 15.
sub.
Ti are coupled to optical fiber 12 at associated bypass portions therealong in each instance by a pair of glass sleeve switches included in each of the node switches.
As is fully disclosed in the above noted patent applications, the two glass sleeve switches in each of the node switches are separated by an optical eraser, which is also known as an optical absorber or attenuator (see application Ser.
No.
750,811, which illustrates the structure of such a device).
The node switch operates to couple fibers 15.
sub.
RJ and 15.
sub.
TJ to fiber 12 via the respective tube switch and to absorb optical energy not tapped into fiber 15.
sub.
RJ where j also is a dummy variable.
The operation of each node switch is controlled by an associated digital control logic arrangement, designated DCL.
sub.
1, DCL.
sub.
2, - - - , DCL.
sub.
N for node switches NS1, NS2, - - - , NSN, respectively.
Each DCL is operative to apply a sustained voltage level, typically 5 or 12 volts to those actuators in the associated node switch.
The three actuators respond to move optical fibers 15.
sub.
R1 and 15.
sub.
TJ into coupling relationship with optical fiber 12 and to move an optical absorber (not shown) into a coupling relationship with fiber 12 also