Device and method to allow for uni-directional traffic on local area networks

[0001] This invention relates to communication devices and methods for local area networks (LAN) involving communication devices and methods for Ethernet uni-directional traffic on LANs.

[0002] Ethernet exists as a combination of twisted pair cables along with fiber optic versions connecting end systems to networks. Ethernet is standardized in IEEE 802.3 for Local Area Network (LAN) protocols. 802.3 exists in several varieties including 10, 100, 1000 Megabytes per Second (Mbps) with physical interfaces supporting bi-directional traffic, that is, transmit and receive traffic. An important characteristic of 802.3 versions is that only duplex systems are supported by the standard as described in 802.3, clause 56, particularly clause 56.1. Accordingly, uni-directional Ethernet is not supported by 802.3.

[0003] Uni-directional Ethernet supports one-way traffic across a single fiber strand. Uni-directional links are useful for applications, such as broadband video services where almost all traffic flow is in one direction. The links conserve bandwidth by enabling the link to be differentially dedicated to transmit and receive interfaces. Also, the number of ports is conserved because the transmit-only and receive-only interfaces act independently.

[0004] The advantages of uni-directional Ethernet may be included under 802.3 by disabling the full duplex requirement of the Media Access Controller (MAC) sub layer in the Data Link Layer supporting the Physical Interface in the Open System Interconnection (OSI) Reference Model. Various alternatives solutions have been used to disable the duplex requirement of the MAC devices including (i) designing non-compliant MAC devices; (ii) providing electrical loop-back of transmit signals to the MAC device, and (iii) providing optical loop-back of transmit signals to the MAC. All of the described alternative solutions are of limited practicality, particularly for small form—factor pluggable modules (SFP) used in Ethernet communications. SFPs are compact, hot-pluggable transceivers used for both telecommunication and data communications and are commercially available from a number of companies including Optical Communication Products (OPC), Woodland Hills, Ca; Canary Communications, Morgan Hill, Ca. and others.

[0005] The present invention brings the advantages of uni-directional Ethernet traffic to 802.3 LANs for extended communication services requiring only the usage/connection of a single fiber and providing a mechanism to maintain a link up condition on a compliant Ethernet MAC device for any hardware that accepts SFP modules. A feed back loop from a MAC device transmit terminal to its receive terminal includes (i) a controlled SFP socket and (ii) a SFP module engaged with the socket, the module including a splitter and active device to maintain the receive terminal in an uplink condition during transmission thereby simulating full duplex communication for 802.3 LAN communications.

[0006] A device and method provide uni-directional Ethernet (UDE) traffic on an 802.3 optical LAN. The UDE signals are delivered to a MAC/PHY device for transmission to the LAN. A small factor form pluggable (SFP) module is activated by a SFP control interface to receive the UDE signals from the MAC/PHY device at a transmit terminal and deliver the signals to a laser within the SFP module. Optionally, an infra red detection device for eye safety purposes may be activated to control turn on the laser after connection of the laser to a optical transmission fiber. The laser transmits the UDE signals to the transmission fiber via a splitter within the SFP module. A portion of the splitter signal activates a photodiode within the module to maintain the receive terminal in an uplink condition during transmission of the UDE to the LAN thereby simulating full duplex operation. Alternatively, the UDE signal maybe looped back directly to the receive terminal to maintain the MAC device in an uplink condition for simulation of the full duplex communication requirement of the 802.3 standard. The SFP control interface deactivates the SFP module, turning off the laser; the photodiode and resetting the infra red detection device, when the UDE transmission is completed.

[0009] Referring to FIG. 1, an exemplary embodiment of a SFP device 100 is shown connected to a printed circuit board 102 and coupled to a MAC/PHY device 104 for providing uni-directional Ethernet (UDE) signals to an optical circuit (not shown) in an IEEE 802.3 LAN. The device or module 100 engages the MAC/Phy device 104 via a standard SFP socket 106. The socket is responsive to an SFP Control Interface 108 for activation/deactivation to receive/terminate series intermediate frequency uni-directional Ethernet (UDE) signals 110 transmitted from the MAC/PHY device 104 via transmit terminal 112 to the module 100 for delivery to the optical LAN (not shown).

[0010] When the socket 106 is activated by the interface 108, under control of an operator (not shown), the series IF—UDE signal 110 is delivered to the SFP module 100, the module including a laser 114, typically a commercially available semiconductor laser; a splitter 120, and a light emitting device 12, typically a standard photo diode. The module delivers the signal 110 to an optical fiber 116. Optionally, a commercially available infra red detection device 118 may be attached to the module 110 for eye safety purposes. The device 118 would be interlocked with the laser to turn on the laser only when the transmit fiber 116 is connected to the laser.

[0011] In one embodiment, the optical splitter 120 splits off and directs a portion of the UDE signal 110 to activate the photo diode device 122 generating and directing light on a receive terminal 124 of the MAC/Phy device 104. Alternatively, the splitter may take place in the electrical domain prior to the laser or photodiode. In any event, the diode light maintains the MAC/PHY device 104 in a link up condition for UDE transmissions on the optical fiber 116 to simulate full duplex communications required by the IEEE 802.3 standard. When the interface circuit 108 is operated to turn off the socket 106, the transmission of UDE optical signals terminates.

[0012] In another embodiment, a loopback connection 128 may be installed and activated in the event the photo diode 122 should fail to operate for UDE transmissions.

[0013] Referring to FIG. 2, a method 200 provides uni-directional Ethernet (UDE) traffic to an IEEE 802.3 LAN.

[0014] An operation 202 initiates UDE signals for delivery to a MAC/PHY device 104 and transmission to an IEEE 802.3 optical LAN (not shown) via an optical fiber 116.

[0015] An operation 204 activates a SFP module 100 via the control circuit 108 to receive the UDE signals from the MAC/PHY device at the transmit terminal 112 and deliver the signals to a first optical device 114 in the SFP module 100.

[0016] Optionally, an operation 206 may activate an infra red detection device 118 to control turn on of a first optical device 114 in the SFP module after connection to the optical fiber 116.

[0017] An operation 208 activates the first optical device 114 to generate and transmit the UDE signals over the optical fiber 116.

[0018] An operation 210 diverts a portion of the UDE signals to a second optical device 122 via a splitter 120 in the SFP module 122.

[0019] An operation 212 transmits light from the second optical device to place the MAC/PHY device in an uplink condition for uni-directional UDE transmissions over the optical fiber.

[0020] An operation 214 continues the light to maintain the MAC/PHY device in an uplink condition during transmission of the UDE signals for simulating full duplex communication to the IEEE 802.3 LAN.

[0021] An operation 216 activates the loopback connection 124 in the event the second optical device fails to operate.

[0022] An operation 218 activates the interface 108 to deactivates the SFP module 100 when the UDE transmission is completed and the process 200 ends, turning off the first and second optical devices, and resetting the infra red detection device.

[0023] All examples and conditional language recited herein are intended for pedagogical objects to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiment (s) of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.