Patent Application
20080267633
Equalizers may be utilized in optical and electrical type systems for example to correct for any channel impairments in the channel or for electronic dispersion compensation (EDC). Typically, such equalizers may be utilized on host boards that include one or more optical transceiver modules that convert signals between optical signals and electrical signals.
Claimed subject matter is particularly pointed out and distinctly claimed in the concluding portion of the specification. However, such subject matter may be understood by reference to the following detailed description when read with the accompanying drawings in which:
It will be appreciated that for simplicity and/or clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, if considered appropriate, reference numerals have been repeated among the figures to indicate corresponding and/or analogous elements.
In the following detailed description, numerous specific details are set forth to provide a thorough understanding of claimed subject matter. However, it will be understood by those skilled in the art that claimed subject matter may be practiced without these specific details. In other instances, well-known methods, procedures, components and/or circuits have not been described in detail.
In the following description and/or claims, the terms coupled and/or connected, along with their derivatives, may be used. In particular embodiments, connected may be used to indicate that two or more elements are in direct physical and/or electrical contact with each other. Coupled may mean that two or more elements are in direct physical and/or electrical contact. However, coupled may also mean that two or more elements may not be in direct contact with each other, but yet may still cooperate and/or interact with each other. Furthermore, the term “and/or” may mean “and”, it may mean “or”, it may mean “exclusive-or”, it may mean “one”, it may mean “some, but not all”, it may mean “neither”, and/or it may mean “both”, although the scope of claimed subject matter is not limited in this respect.
Referring now to
Electrical interface 112 may have a data bus where the width of the data bus varies depending on the type of form factor and/or Multi-Source Agreement (MSA) for which optical transceiver module 100 is intended. For example, the data bus may comprise a 1-bit differential bus, a 4-bit differential bus, a 16-bit differential bus, and so on. Electrical interface 112 may also provides direct-current (DC) connections to the DC power supplies of the host board.
In one or more embodiments, controller 114 may implement a control system for optical transceiver module 100. Controller 114 may perform multiple functions that previously had been implemented using analog hardware. Controller 114 may set control parameters for the Physical Medium Attachment (PMA) 116, receiver (RX) 118 and/or transmitter (TX) 120, which may include operational parameters that may vary over time and/or temperature and/or when the host system changes the link configuration, for example loopback modes. In one or more embodiments, controller 114 may also provide a two-wire interface such as I2C so the host board can set control parameters and read the status registers where monitor values are stored, although the scope of the claimed subject matter is not limited in these respects.
Physical medium attachment (PMA) 116 may provide core electrical functionality for optical transceiver module 100, for example to maintain robust signal integrity at higher data rates. In one or more embodiments, PMA 116 may include a clock multiplier/multiplexer (MUX/CMU) circuit and clock and data recovery/demultiplexer (CDR/DEMUX) circuit. The MUX/CMU circuit interleaves the 16-channel data bus into a serialized data stream at the line rate, clocked by a multiplied version of the input clock. This data stream is used to modulate transmitter 120. The CDR/DEMUX circuit provides the complementary functionality on the receive side for receiver 118.
In one or more embodiments, receiver 118 may comprise a device capable of converting an incoming optical signal 124 into an electrical signal. Likewise, transmitter 120 may comprise a device capable of converting an electrical signal into an outgoing optical signal 126. The type of devices utilized for receiver 118 and transmitter 120 may depend upon the reach requirements of the fiber link for the optical signals. For example, for Very Short Reach (VSR) applications in the enterprise space, such as within-building or within-campus a gallium arsenide/aluminum gallium arsenide (GaAs/AlGaAs) type Vertical Cavity Surface Emitting Laser (VCSEL) may be utilized as the optoelectronic device for transmitter 120. For receiver 118, a GaAs type positive-intrinsic-negative (PIN) photodetector may be utilized. For Longer Reach (LR) links on the order of about 7-20 kilometers, transmitter 120 may include an indium phosphide (InP) based single-mode Distributed Feedback Laser (DFB) operating for example at 1310 nm. For metro area network access, extended reach (ER) links on the order of about 40-80 kilometers may be utilized. In such embodiments, a DFB laser combined with an Electro-Absorption Modulator (EAM) on an InP substrate may be utilized. Receiver 118 may include an InP type device or gallium arsenide (GaAs) PIN type photodiodes, or an InP Avalanche Photodiodes (APD) type device, to convert light into electrical current, for example. However, these are merely examples of optical-electrical devices that may be utilized for receiver 118 or transmitter 120, and the scope of the claimed subject matter is not limited in these respects.
Referring now to
In one or more embodiments, optical transceiver module 100 may include a feed forward equalizer (FFE) type linear equalizer 216 that couples with a linear and non-linear equalizer 218 disposed on host board 218. In such an arrangement, part of the equalization for electrical signal path 212 may be performed on optical transceiver module 100 by FFE linear equalizer 216, and part of the equalization for electrical signal path 122 may be performed on host board 200 by linear and non-linear equalizer 218. Such an arrangement may be generally referred to as a split equalization arrangement, however the scope of the claimed subject matter is not limited in this respect. In one or more embodiments, FFE linear equalizer 216 may comprise a non-retimed type filter, and linear and non-linear equalizer 218 may comprise a re-timed decision feedback type filter. FFE linear equalizer 216 may work in unison with linear and non-linear equalizer 218, and may be fully and/or at least partially controlled by instructions executed by controller 222, which may be disposed on host board 200, via control lines 224 and 226. As a result, linear and non-linear equalizer 218 is not required to be a full equalizer and/or not required to perform all of the equalization for electrical signal path 122. For example, a full long reach standard for multimode fiber (LRM) type equalizer operating at multiple ports of host board 200 may not be required for host board 200 in one or more embodiments. By disposing FFE linear equalizer 216 only in modules that may require additional equalization, for example for a 10G-LRM type link, linear and non-linear equalizer 218 on host board may be realized via simpler and less complex equalizers, while allowing for more complex equalization one channels that may benefit from higher equalization by utilization of two equalizers in a split equalization arrangement as shown in
In one or more embodiments, host board 200 may comprise a device capable of utilizing optical transceiver module 100 to communicate vial optical signals such as utilized in various telecommunications and/or networking type applications. For example, host board 200 may comprise a backplane for example as part of a server, a switch line card, an Ethernet or Gigabit Ethernet type card, or as part of a storage area network (SAN) for example a Fibre channel type system or the like. Furthermore, host board 200 may comprise a broadband wireless network type baseband board or the like for example for a Worldwide Interoperability for Microwave Access (WiMAX) type network. However, these are merely examples for host card 200, and the scope of the claimed subject matter is not limited in these respects.
Although the claimed subject matter has been described with a certain degree of particularity, it should be recognized that elements thereof may be altered by persons skilled in the art without departing from the spirit and/or scope of claimed subject matter. It is believed that the subject matter pertaining to split equalization function for optical and electrical modules and/or many of its attendant utilities will be understood by the forgoing description, and it will be apparent that various changes may be made in the form, construction and/or arrangement of the components thereof without departing from the scope and/or spirit of the claimed subject matter or without sacrificing all of its material advantages, the form herein before described being merely an explanatory embodiment thereof, and/or further without providing substantial change thereto. It is the intention of the claims to encompass and/or include such changes.
