Abstract:
An optical transmission bypass device attaching a network device to a fiber optic network allows fiber optic transmissions to bypass the network device when not powered, thereby maintaining continuity of the fiber network. A first and second actuating optical reflector has a reflective face that, in an un-powered state, is disposed to place the reflective face of the actuating optical reflector in a first position with respect to an optical path of an optical port, and, in a powered state, is disposed to place the reflective face of the actuating optical reflector in a second position with respect to the optical path of the optical port.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates generally to optical networks. More particularly, the present invention relates to transmission bypass techniques in fiber optic networks. 
     2. Description of the Related Art 
     Fiber optic networks are used in a variety of applications. In some applications, such as signal routing in a device interconnection network, devices connected to the fiber optic network are interconnected in series such that the output from each device is connected to the input of another device, such that the fiber optic network forms a loop network. However, a problem arises in such networks when one of the devices connected to the network is not powered on or fails. This essentially breaks the loop or chain network and prevents the network devices on either side of the powered-down device from communicating. It would be desirable to provide a network device that allows fiber optic transmission even when not powered. 
     SUMMARY OF THE INVENTION 
     An optical transmission bypass device attaching a network device to a fiber optic network allows fiber optic transmissions to bypass the network device when not powered, thereby maintaining continuity of the fiber network. The optical transmission bypass device comprises a first and second optical port, a first and second actuating optical reflector and an optical transmission line. The first optical port is optically coupled to a first optical transmission line, and the second optical port is optically coupled to a second optical transmission line. The first actuating optical reflector has a reflective face that, in a first state, is disposed to place the reflective face of the first actuating optical reflector in a first position with respect to an optical path of the first optical port, and, in a second state, is disposed to place the reflective face of the first actuating optical reflector in a second position with respect to the optical path of the first optical port, wherein the first actuating optical reflector is in the first state when the first actuating optical reflector is not electrically powered. The second actuating optical reflector has a reflective face that, in the first state, is disposed to place the reflective face of the second actuating optical reflector in a first position with respect to an optical path of the second optical port, and, in the second state, is disposed to place the reflective face of the second actuating optical reflector in a second position with respect to the optical path of the second optical port, wherein the second actuating reflector is in the first state when the second actuating optical reflector is not electrically powered. The optical transmission line is positioned between the first actuating reflector and the second actuating reflector, wherein, in the first state: the optical transmission line is optically coupled at a first end to the first optical port by the reflective face of the first actuating optical reflector and optically coupled at a second end to the second optical port by the reflective face of the second actuating optical reflector, such that received optical transmission data at the first optical port is reflected from the first reflective face of the first actuating optical reflector into the first end of the optical transmission line and out of the second end of the optical transmission line and reflected from the second reflective face of the second actuating optical reflector to the second optical port to provide the received optical transmission data for transmission by the second optical transmission line. In the second state, the optical transmission line is not optically coupled at a first end to the first optical port by the reflective face of the first actuating optical reflector and not optically coupled at a second end to the second optical port by the reflective face of the second actuating optical reflector. 
     In an alternative embodiment, in the second state, the reflective face of the first actuating optical reflector in the second position with respect to the optical path of the received optical transmission data is positioned such that the reflective face of the first actuating optical reflector is outside the optical path of the received optical transmission data, allowing the received optical transmission data at the first optical port to pass directly to a receiver, and the reflective face of the second actuating optical reflector in the second position with respect to the optical path of the optical transmission data provided by the second optical port to the second optical transmission line is positioned such that the reflective face of the second actuating optical reflector is outside the optical path of the optical transmission data provided by the second optical port, allowing optical transmission data from a transmitter to pass directly to the second optical port. 
     The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 depicts a data processing system network in which a preferred embodiment of the present invention may be implemented; and 
     FIG. 2 is an optical bypass device in accordance with a preferred embodiment of the present invention; 
     This invention is described in a preferred embodiment in the following description with reference to the figures, in which like numbers represent the same or similar elements. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is an illustration of a ring network  6 , which comprises a multiplicity of nodes  1 ,  2 ,  3  and  4 , connected in serial fashion. The node numbered “ 4 ” represents the “nth” node, so that there can be any number of nodes attached to the ring. A connector  5  serves as the interface between the ring and node. The connector  5  can route optical information in either of two ways. This is illustrated in FIG. 1 by showing one connection as block  5   a  and the other as block  5   b , with blocks  5   a  and  5   b  connected to node blocks  3   a  and  3   b , respectively. It should be understood that a single node  3  and single connector  5  are in fact employed. The normal optical information flow from the ring  6 , across the connector  5 , to the node  3 , across the connector  5  and back to the ring, known as the cross-state of the connector, is illustrated by connector block  5   a . If a node fails, loses power or is disconnected, the ring will fail unless continuity of the ring is maintained. As illustrated by connector block  5   b , upon failure or disconnection of node  3 , the node is bypassed by optical loopback, which is referred to as the bypass-state. Optical loopback is achieved by incorporating an optical bypass device, in accordance with a preferred embodiment of the present invention discussed below, into various fiber optic connectors. 
     FIG. 2 shows an exemplary embodiment of an optical bypass device  102 . Optical bypass device  102  includes a silicon block  104  and lenses  116 ,  118 . Silicon block  104  has built therein micro-electrical-mechanical systems (MEMS) mirrors  106 ,  108 , ball lenses  110 ,  112  and fiber stub  114 . MEMS mirrors  106 , 108  are micro-actuated devices mounted with precision micro-mirrors. 
     The optical bypass device  102  operates in two states that are defined by the position of MEMS mirrors  106 ,  108 . As described in more detail below, optical signals entering the optical bypass device  102  from fiber optic cable  120  are directed to follow different paths in those two states. A controlled voltage or current source, not shown, can be used to control the action of the MEMS mirrors  106 ,  108  in enabling one or the other of the two states. 
     Fiber optic cable  120  is a duplex cable having a receive (RX) portion  122  and a transmit (TX) portion  124 . For example, optical fibers  128 ,  132  may be glass 62.5/125 multi-mode fibers. Receive portion  122  contains a ferrule  126  housing an optical fiber  128 . Transmit portion  124  contains ferrule  130  housing optical fiber  132 . Fiber optic cable  120  is fixedly attached to optical bypass device  102 . A ferrule is a mechanical fixture, generally a rigid tube, used to confine the stripped end of a fiber bundle or a fiber. Receive portion  122  is mounted on optical bypass device  102  such that optical fiber  128  is aligned with optical axis  134 , and such that transmit portion  124  is mounted on optical bypass device  102  to align optical fiber  132  with optical axis  138 . 
     MEMS mirrors  106 , 108  are designed to be deployed as shown in FIG. 2 in the power-offstate. The power-off state (unpowered) occurs when optical bypass device  102  is not receiving power at the MEMS mirrors  106 ,  108 . Thus, when power is not applied to MEMS mirrors  106 ,  108  they reset to an initialization position. In a preferred embodiment, they have their mirror surfaces  140 ,  142 , respectively, aligned at a 45 degree (45°) angle to optical axis  134 ,  138 , respectively. When optical bypass device  102  receives optical transmissions over optical fiber  132 , the optical transmissions are reflected at a 45° angle from mirror face  142  and enter ball lens  112 . Ball lens  112  focuses the optical transmission into a first end of fiber stub  114 . Fiber stub  114  transmits the optical transmission through its length and out a second end to be received by ball lens  110 . Ball lens  110  focuses the optical transmission onto mirror face  140  of MEMS mirror  106 . MEMS mirror  106 , being angled at a 45° angle to optical axis  134 , reflects the optical transmission directly into optical fiber  128 . 
     When power is applied to optical bypass device  102 , MEMS mirrors  106 , 108  are deployed in the power-on state (powered), whereby MEMS mirrors  106 ,  108  rotate to place mirror faces  140 ,  142  parallel to optical axis  134 ,  138 , respectively, and in such a manner as to place MEMS mirrors  106 ,  108  outside of the optical path of optical transmissions over optical fibers,  128 , 132  and along optical axes  134 ,  138 , respectively. Therefore, when optical bypass device  102  is powered and MEMS mirrors  106 ,  108  are deployed in the power-on state, optical transmissions are transmitted through optical fiber  128  along optical axis  134 , through lens  116 , and into additional optical processing components (not shown) within optical bypass  102  or the network device attached to optical bypass device  102 . Optical transmissions transmitted by optical bypass device  102  or an attached network device are transmitted along optical axis  138 , through lens  118 , to be focused at the entrance of optical fiber  132 , and thereby transmitted through the transmit portion  124  of optical fiber  120 . 
     As implemented in a preferred embodiment, fiber cable  120  would be part of a fiber optic network transmitting and receiving optical transmission data from a transceiver system incorporating optical bypass device  102 . In the system shown in FIG. 1, ring network  6  would include fiber cable  120  and connector  5  would comprise optical bypass device  102 . When the system incorporating optical bypass device  102  is operating correctly and is properly powered, optical bypass device  102  operates in the cross-state of the connector, thereby allowing optical transmission to and from the system through lenses  116 ,  118 . This is accomplished by actuating MEMS mirrors  106 , 108  in the power-on state into position outside of the optical path of optical fibers  128 ,  132  along optical axes  134 ,  138 . 
     Upon failure or disconnection of node  3  (for example, by the network device being turned off or un-plugged from the optical bypass device), optical bypass device  102  maintains ring continuity with ring network  6  by providing the optical loop back of the bypass-state. The bypass-state is characterized by MEMS mirrors  106 ,  108  being deployed in the power-off state such that they are aligned at a 45° angle to optical axes  134 ,  138 . This creates the optical loop back along the optical path formed by optical fiber  128  to MEMS mirror  106 , to ball lens  110 , to fiber stub  114 , to ball lens  112 , to MEMS mirror  108  and finally to optical fiber  132 . 
     While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.