Patent Application
20120045202
This application claims the benefit of Chinese Patent Application Nos. 201010254908.7 and 201010290187.5, filed on Aug. 17, 2010 and Sep. 25, 2010, respectively, and each of which is incorporated herein by reference as if fully set forth herein.
The present invention generally relates to the field of optical data communications and network technology. More specifically, embodiments of the present invention pertain to a high speed, bi-directional optical network transceiver, particularly circuits, devices and an optical network unit (ONU) therefor, and method(s) of making and/or using the same. In one embodiment, the transceiver is a small form factor pluggable (e.g., SFP+ compatible) 10 G Ethernet passive optical network (EPON) transceiver. Embodiments of the present invention also pertain to a 10 G bi-direction transceiver with an energy-saving function, circuits and devices therefor, and method(s) of making and/or using the same.
With the popularization of FTTX technology, the wide availability of high-speed bandwidth has beneficially transformed society. For example, SOHO technology provides accessible high-definition interactive video programs, telemedicine and remote education. As demand for bandwidth increases, existing 1 G EPON technology is not ideally suited to meet today's needs. Furthermore, the circuits and optics of conventional 10 G technology consume excessive power, which can affect normal communication. Thus, the higher bandwidth of the 10 G EPON ONU transceivers and the ability to reduce energy consumption are attractive solutions to problems related to insufficient bandwidth and excessive consumption of power in optical networks.
In transceivers, detecting input optical power and output optical power may allow users to obtain real-time monitoring information of the transceiver, and ensure adequate performance and proper operation. In traditional continuous-mode transmitters, optical power data is derived from a monitor photodiode (MPD) current, wherein the MPD current is approximately proportional to the output optical power. However, during a burst mode of operation, the laser is on and provides light for a relatively brief duration of time, which can vary from one moment in time to the next. Thus, it can be difficult to quickly and accurately indicate the output optical power and value. Additionally, since the optical signal (e.g., the laser) operates at a rate of 10 Gb/s, it can still be problematic to ensure the receiver (RX) receptivity and the ability to monitor the RX optical power in real time. Thus, the burst mode of operation conforms to this time sequence (e.g., 10 Gs/s) and the transmitter (TX) communication index of the 10 G EPON system simultaneously.
Furthermore, with existing 10 G solutions, it is difficult to reduce instantaneous power consumption in the 10 G circuit and optics. For example, as shown in
The present disclosure overcomes disadvantages of the existing technology (e.g., insufficient bandwidth and excessive consumption of power). Advantages of the present bi-directional transceiver include a low design cost, a simple circuit design that makes use of system silence to save energy and reduce consumption without affecting normal communication of the optical network (e.g., a 10 G EPON system) and that provides a real-time indication of the burst-mode optical output power.
Embodiments of the present invention relate to a high-speed and/or power-saving bi-directional transceiver comprising a burst laser driver; a burst output power monitoring and indicating circuit; control logic (e.g., a microcontroller unit); bi-directional optics; an avalanche photodiode (APD) bias control circuit; a limiting amplifier; and a receiver optical power monitoring circuit. Optionally, the present transceiver includes (and is packaged in) a small form factor pluggable (SFP+) connector housing. The present ONU transceiver provides an effective solution to reduce energy and/or power consumption during a silent operational mode, without significant adverse effects on normal communications in the PON system.
Various embodiments of the present invention also relate to a high-speed and/or energy-saving bi-directional transceiver comprising a transmitter (TX) burst energy-saving circuit; a TX burst holding circuit; a receiver (RX) continuous energy-saving circuit; a RX continuous holding circuit; and control logic (e.g., a microcontroller, microprocessor, signal processor, ASIC, etc.) configured to control one or more of the TX burst energy-saving circuit, TX burst holding circuit, RX continuous energy-saving circuit and RX continuous holding circuit. In accordance with a dynamic time slot, the TX energy-saving circuit turns off all functional components of the transmitter during an idle time (e.g., when the transmitter enters an idle or stand-by mode), and together with the burst holding circuit, quickly resumes normal functions during working time (e.g., when the transmitter is to enter an operational mode). The continuous RX energy-saving circuit quickly turns off the receiver circuitry during a silent time (e.g., an idle or stand-by mode) and, together with the RX burst holding circuit, enables the receiver to resume the work state (e.g., an operational mode) according to the system requirements. The control logic saves an RX status and provides access to and/or by energy-saving software.
In various embodiments of the present invention, a laser capable of operating in a burst mode and the burst laser driver are able to output an optical signal satisfying both a time-multiplexing sequence and the optical communication requirements for 10 G EPON communication systems by control of external control logic. The burst output power monitoring and indicating circuit allows real-time indications and monitoring of the optical signals with varying burst duration. The internal control logic (e.g., an MCU), which may store information for a common commercial operating temperature range (e.g., of about 0° C. to about 70° C.) of the laser, compensates for or controls the temperature-dependent variation(s) in laser output by providing (i) a bias current and a modulation current to the laser and (ii) a bias voltage of the APD via a sampling circuit, which ensures that the optical functions are not affected by temperature, thereby meeting signal transmission requirements in burst mode and receiver signal requirements in continuous mode.
Under the control of the burst control logic, the burst laser driver and the laser can convert a 10 gigabyte per second (Gb/s) electrical signal to a stable optical signal within nanoseconds. The burst output power monitoring and indicating circuit is configured to indicate the power and the level or wavelength of the transmitted optical signal.
The receiver generally comprises the APD and a transimpedance amplifier (TIA), which are used for high-speed conversion of the received optical signal to a low-voltage electrical signal. Subsequently, the signal is reformatted, and the received data (RXD) is amplified with a limiting amplifier that may have a clock recovery function to provide an electrical output and an optional recovered clock. The clock recovery function ensures that the output signal satisfies the requirements of a 10 G EPON RX signal with respect to amplitude and fluctuation(s). Furthermore, the limiting amplifier enables indication of a RX signal by providing a high-level signal when the input signal is within an acceptable range.
Compensation for the optical output power, the modulation current of the laser, and the bias voltage of the APD over an entire (e.g., predetermined) temperature range is performed via the control logic (e.g., MCU). First, the correlation between a compensation value for the optical output power, modulation current, and/or bias voltage based on the temperature is obtained through testing (e.g., empirical testing and/or calibration). Second, a lookup table is created (e.g., in memory associated with and/or accessible by the control logic) according to the correlation. Lastly, the control logic compensates, in real time, for the temperature-dependent variations in the optical power output, the modulation current of the laser, and the bias voltage of the APD throughout an entire predetermined temperature range according to the lookup table.
With respect to conventional technology, the present invention provides a burst laser driver and an RX limiting amplifier capable of operating in a 10 Gb/s network, integrated on a single chip to reduce the cost of the components and the layout space/area of the design. Secondly, the burst laser driver controls the burst signal output of the laser via the control logic and provides an automatic power control loop that allows for current sampling. Deterioration of the optical power due to laser aging is reduced, and burst laser performance can be regulated and adjusted without additional external circuitry (e.g., switching logic and analog sampling circuitry). To realize system performance reporting, the burst optical power indicating circuit and the control logic monitor the burst power, so as to realize system performance reporting. The present limiting amplifier with RX signal indication circuitry and optional clock recovery circuitry satisfies the requirements of 10 Gb/s optical networks with respect to the signal amplitude and fluctuation, ensuring accurate transmission of the optical signals and accurate monitoring of the RX optical signals.
In various embodiments of the present invention, Optical Line Termination (OLT) bandwidth is allocated by time division multiplexing (TDM; e.g., burst TDM) in an uplink PON system, in which the TX (or circuits thereof) can be turned off by the TX burst energy-saving circuit. When the TX function (e.g., the uplink transmission) is idle, the TX burst holding circuit (e.g., in response to a respective control signal provided by the PON system) turns off the transmitter or a number of circuits in the transmitter, saving energy in and the operational status of the transmitter. When uplink transmissions and/or communications are needed, the transmitting function of the ONU transceiver can be quickly resumed according to the saved operational status.
Optionally, the ONU transceiver may receive OLT downlink service (e.g., data, instructions, etc.). When downstream operations and data are not received by the system, the RX (and/or circuits thereof) can be turned off according to the respective control signal from the PON system, saving energy in and the operational status of the receiver. When downlink operations are needed, the receiving function of the ONU transceiver can be quickly resumed according to the saved operational status.
The control logic in the ONU transceiver is configured to provide control signals to the respective circuits in the transmitter or receiver according to the system control logic. The internal control logic saves operational status information of the TX and/or RX to ensure interoperation of all functional circuits. Furthermore, the control logic may provides to an interface control register energy-saving software to realize a real-time monitor for the ONU transceiver in both the energy-saving (e.g., power-down, stand-by or idle) and working (e.g., operational) modes.
Compared to conventional 10 G ONU technology, the present invention advantageously provides one or more energy-saving control circuits that reduce maximal consumption during transceiver silence, and are capable of switching parts of the transceiver to working or energy-saving modes (e.g., according to external system control logic), ensuring normal communications. The internal control logic (e.g., a microcontroller) can efficiently coordinate all transmitter and receiver functional circuits and allow operational status inquiries. Thus, the present invention overcomes the disadvantage of high power consumption in existing 10 G symmetrical ONU technology, and provides an energy saving circuit for bi-directional transceivers to effectively reduce energy consumption of ONUs in a PON system (e.g., a 10 Gb/s EPON system).
These and other advantages of the present invention will become readily apparent from the detailed description of various embodiments below.
Reference will now be made in detail to various embodiments of the invention, examples of which are illustrated in the accompanying drawing(s). In order to achieve the objectives, technical solutions and advantages of the present invention more clearly, further details of the invention are described below with regard to the Figure(s). While the invention will be described in conjunction with the following embodiments, it will be understood that the descriptions are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be readily apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present invention. The embodiments described here are only used to explain, rather than limit, the invention.
Furthermore, all characteristics, measures or processes disclosed in this document, except characteristics and/or processes that are mutually exclusive, can be combined in any manner and in any combination possible. Any characteristic disclosed in the present specification, claims, Abstract and Figures can be replaced by other equivalent characteristics or characteristics with similar objectives, purposes and/or functions, unless specified otherwise. Each characteristic is generally only an embodiment of the invention disclosed herein.
For the sake of convenience and simplicity, the terms “connected to,” “coupled with,” “coupled to,” and “in communication with” (which terms also refer to direct and/or indirect relationships between the connected, coupled and/or communicating elements, unless the context of the term's use unambiguously indicates otherwise) are generally used interchangeably herein, but are generally given their art-recognized meanings
In various embodiments, and referring now to
Referring to
In various embodiments, a 10 G RX electrical signal is transmitted through the SFP+ connector 206. Subsequently, the burst laser driver in unit 201 outputs a modulated signal and a bias current for the BOSA 203, according to one or more predetermined or preprogrammed settings of the control logic 202 to obtain an optical signal satisfying the optical power and the extinction ratio of the system (e.g., system 100 of
The burst laser driver in unit 201 converts modulated voltage signals (e.g., from the host device via connector 206) into a current signal, which drives the laser in the BOSA 203 and generates an optical signal that can be transmitted to a local optical line terminal (OLT) via a fiber. The potential energy of the optical signal is controlled by a logic level signal transmitted to a TX_BRST pin in the connector 206. In certain embodiments, the generation and turn-off time of the TX_BRST signal (which controls entry into and exit from a burst communication mode) are in accordance with one or more standards (e.g., IEEE P802.3av).
In various embodiments, the BOSA 203 comprises a laser and an APD having optical communication wavelengths centered at 1270 nm and 1577 nm, respectively. The intensity of the optical signal converted from the laser and the electric signal amplitude converted from the optical signal by the APD are closely related to the temperature of the laser and the APD, respectively. With the same driving current and APD bias voltage, both laser output optical power and amplitude of the APD electrical output signal decrease with an increase in temperature. To ensure proper characteristics of the optics and to satisfy the optical fiber communication requirements in a commercially accepted temperature range, the control logic 202 compensates for the laser drive current and APD bias current according to the temperature of the laser and the APD, respectively. Consequently, the present transceiver may further include one or more temperature sensors (e.g., temperature sensing circuits) configured to detect the temperature of the laser and/or the APD, and communicate the same to the control logic 202.
Specifically, the control logic 202 compensates for temperature-based variations in the laser current and the APD bias current by utilizing a look-up table. Compensation for the laser current comprises adjusting one or more working currents of the laser, which in some embodiments, include a bias current and a modulation current. By utilizing AC coupling, detecting the bias current can determine the output power by a predetermined or empirically-determined correlation, and detecting the modulation current can determine an extinction ratio by a similarly predetermined or empirically-determined correlation. Thus, two different look-up tables may be included to determine the amount of compensation to be provided to the laser in response to the laser temperature information.
To obtain a desired current value, the laser is operated over the entire commercial operating temperature range of the laser (e.g., approximately 0° C. to about 70° C.) at intervals of, e.g., 3 to 5° C., and the output power and/or wavelength data is analyzed. The power and extinction ratio of the optical output signal are also monitored for stability. The current value output by the control logic 202 instructs the laser driver in unit 201 to output an analog voltage (which may vary according to the temperature of the laser in BOSA 203) using a digital-to-analog converter (DAC) in the control logic 202. Thus, the correlation between the temperature of the laser in BOSA 203 and the current value depends on the correlation between the temperature and a predetermined DAC value. Many predetermined DAC values may be obtained to perform and/or implement the correlation.
To more readily obtain the correlation, key temperature points, which include a minimum of 3 temperature points (e.g., 0° C., 25° C. and 70° C.) can be selected to obtain a set value corresponding to the optical power and extinction ratio at each temperature. According to the linear unity of temperature and a plurality of set values corresponding to various temperature values at a predetermined interval (e.g., 3° C., 5° C., or another value that may be appropriate for a given application) can be determined. A look-up table matching the temperature value and the corresponding DAC value at every predetermined temperature point within the working temperature range (e.g., approximately 0° C. to about 70° C.) can be created accordingly. In one embodiment, the table can be stored in a nonvolatile memory (e.g., a flash memory) associated with and/or accessible by the control logic 202 so that the system 200 retains the data in the event of power interruption and/or failure.
In addition, real-time transceiver temperature information of the transceiver (e.g., the laser in BOSA 203) is sent to the control logic 202, which determines the digital current value corresponding to the power and extinction ratio from the look-up table, and subsequently enters the digital current value into a control register of the DAC. Compensation for the APD bias current is conducted similarly to the laser power. However, one difference is that the DAC (which, in one embodiment, can be a second DAC in the control logic 202) controls a relatively high output voltage generated by an APD booster circuit in APD block 205, so that the look-up table shows a correlation between the temperature of the APD in block 205 and the APD bias current. Subsequently, the control logic 202 sets the APD bias current via a DAC according to the temperature information (obtained by real-time monitoring of the APD 205) and the look-up table that shows the correlation between the temperature and the DAC value.
In various embodiments of the present invention, the transceiver 200 provides a real-time indication of a transmitter slow-down or shut-down indicator (e.g., the TX_SD output) and a transmitter power monitor signal (e.g., the TX_Power_Mon output) in burst mode operations. In addition, the transceiver 200 may provide a receiver activity signal (e.g., the RSSI output) in a continuous operational mode. The receiver activity signal may indicate that the receiver (i) is actively receiving an optical input signal, (ii) has not received an optical input signal for a predetermined period of time (e.g., 1 μsec-100 msec), or (iii) both (i) and (ii).
Referring to
In addition, the RX input signal power is monitored by a photodiode 311 in the APD booster circuit, and the RX power monitoring circuit 416 (
The energy-saving circuit of the EPON ONU transceiver 500 shown in
The RX amplification and rectification circuit 503 of
Referring to
The exemplary EPON ONU transceiver with energy-saving TX and RX functions (e.g., as depicted with regard to
However, energy saving at the receiver (e.g., receiver 700 in
Referring to
Thus, the present invention provides a high speed, bi-directional optical network transceiver, particularly circuits and devices therefor, and method(s) of making and/or using the same. In one embodiment, the transceiver is a 10 G Ethernet passive optical network (EPON) transceiver, and in another embodiment, the transceiver is housed or enclosed in a small form factor pluggable (SFP or SPF+) compliant package. Embodiments of the present invention also provide a 10 G bi-direction transceiver with energy-saving functions, circuits and devices therefor, and method(s) of making and/or using the same.
The high-speed bi-directional transceiver generally comprises a burst laser driver; a burst output power monitoring and indicating circuit; control logic (e.g., a microcontroller unit); bi-directional optics; a photodiode bias control circuit; a limiting amplifier; and a receiver optical power monitoring circuit. Optionally, the present transceiver includes (and is packaged in) a small form factor pluggable (SFP+) connector housing. The present ONU transceiver provides an effective solution to reduce energy and/or power consumption during a silent operational mode, without significant adverse effects on normal communications in the PON system.
Furthermore, the energy-saving bi-directional transceiver generally comprises a transmitter (TX) energy-saving circuit; a TX burst holding circuit; a receiver (RX) energy-saving circuit; a RX continuous holding circuit; and control logic (e.g., a microcontroller, microprocessor, signal processor, ASIC, etc.) configured to control one or more of the TX energy-saving circuit, TX burst holding circuit, RX energy-saving circuit and RX continuous holding circuit. In accordance with one or more control signals, the TX energy-saving circuit turns off some or all functional components of the transmitter during an idle time (e.g., when the transmitter enters an idle or stand-by mode), and together with the burst holding circuit, quickly resumes normal functions during working time (e.g., when the transmitter is to enter an operational mode). The RX energy-saving circuit quickly turns off one or more blocks of the receiver circuitry during a silent time (e.g., an idle or stand-by mode) and, together with the RX burst holding circuit, enables the receiver to resume a working state (e.g., a normal operational mode) according to system requirements. The control logic is also capable of saving the TX and/or RX working status, and provides access to and/or by energy-saving software.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201010254908.7 | Aug 2010 | CN | national |
| 201010290187.5 | Sep 2010 | CN | national |
