Multifunctional laser diode driving circuit, a module comprising the same, and a method using the same

Abstract

A multifunctional laser driving circuit, and an optical module and method of using the same, are disclosed. The circuit combines first and second optical signals having different functions to form a compound signal, and switches among the first optical signal, second optical signal and compound signal by enabling or disabling first and second laser drivers corresponding to the first and second optical signals. The circuit can provide functions to optical modules, including converting an electrical data signal into an optical data signal; converting an electrical line monitoring signal into an optical line monitoring signal; combining the optical data and line monitoring signals and synchronously transmitting them to a fiber; and providing an OTDR function. Relative to using external OTDR tools to detect line faults, the present circuit and method enables simple line connection, timely detection of lines faults, and low costs of implementation.

Claims

1. A method of driving a laser diode (LD), comprising: enabling or disabling driving the LD using first and second electrical signals and first and second laser drivers; generating a first optical signal with the LD when the first electrical signal enables driving the LD, and generating a second optical signal with the LD when the second electrical signal enables driving the LD, wherein the first optical signal is transmitted when the first laser driver is enabled and the second laser driver is disabled, the second optical signal is transmitted when the first laser driver is disabled and the second laser driver is enabled, the first optical signal has a first frequency, and the second optical signal has a second frequency less than the first frequency; combining the first optical signal and the second optical signal into a compound signal, wherein the compound signal is output when the first laser driver and the second laser driver are enabled; and outputting the first optical signal, the second optical signal, and the compound signal from the LD over a same optical transmission medium.

2. The method of claim 1, wherein said first optical signal is a data signal, said second optical signal is a line monitoring signal or a line detection signal, and said second optical signal is said line detection signal when the optical transmission medium does not work properly, or a user or a network comprising the optical transmission medium instructs a transmitter comprising the LD to detect faults in the optical transmission medium.

3. The method of claim 2, further comprising regulating a frequency of the line detection signal to increase an accuracy of detecting the faults in the optical transmission medium.

4. The method of claim 2, further comprising increasing an output strength of the line detection signal.

5. The method of claim 4, wherein increasing the output strength of the line detection signal comprises increasing an output power of the second laser driver.

6. The method of claim 1, further comprising driving the laser diode with the first laser driver according to an electrical data signal, and driving the laser diode with the second laser driver according to an electrical line monitoring signal.

7. The method of claim 1, wherein said first and second laser drivers are enabled or disabled with a controller.

8. The method of claim 1, further comprising recovering the second optical signal by detecting an average optical power of the second optical signal.

9. A multifunctional laser driving circuit, comprising: a signal transmitter module comprising a laser, a controller electrically connected to said signal transmitter module, a first laser driver receiving a first enable/disable signal from the controller and providing a first electrical signal to the laser, and a second laser driver receiving a second enable/disable signal from the controller and providing a second electrical signal to the laser, wherein said laser is configured to (i) convert said first electrical signal to a first optical signal when the first laser driver is enabled and the second laser driver is disabled, the first optical signal having a first frequency, (ii) convert said second electrical signal to a second optical signal when the first laser driver is disabled and the second laser driver is enabled, the second optical signal having a second frequency less than the first frequency, (iii) combine said first and second optical signals into a compound signal when the first laser driver and the second laser driver are enabled, and (iv) transmit the first optical signal, the second optical signal, and the compound signal over a same optical transmission medium.

10. The circuit of claim 9, wherein said first electrical signal is an electrical data signal, said second electrical signal is an electrical line monitoring signal, said first optical signal is an optical data signal, and said second optical signal is an optical line monitoring signal.

11. The circuit of claim 10, wherein said second optical signal is a line detection signal when an optical transmission medium configured to receive said optical data signal and said optical line monitoring signal does not work properly, or a user or a network comprising the optical transmission medium instructs the laser driving circuit to detect faults in the optical transmission medium.

12. The circuit of claim 9, said controller comprises a microcontroller.

13. The circuit of claim 9, wherein said signal transmitter module comprises a transmitter optical subassembly (TOSA).

14. The circuit of claim 9, wherein the compound signal has a modulation depth of from 5% to 50%.

15. The circuit of claim 9, further comprising an inter-integrated circuit (IIC or I2C)-compliant bus connected to the signal transmitting module and the controller, and configured to transmit signals between the signal transmitting module and the controller.

16. The circuit of claim 9, wherein the controller controls (i) transmission of the first optical signal by enabling the first laser driver and disabling the second laser driver, (ii) transmission of the second optical signal by disabling the first laser driver and enabling the second laser driver, and (iii) transmission of the combined signal by enabling the first laser driver and the second laser driver.

17. The method of claim 1, wherein the compound signal has a modulation depth of from 5% to 50%.

18. The method of claim 1, wherein the second frequency is at least ten times less than the first frequency.

19. The circuit of claim 9, wherein the second frequency is at least ten times less than the first frequency.

20. The circuit of claim 19, wherein the first frequency is from 1 MHz to 1 THz, and the second frequency is from 1 kHz to 1 GHz.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a block diagram showing an exemplary multifunctional optical signal transmission apparatus in accordance with one or more embodiments of the present invention.

(2) FIG. 2 is a waveform diagram showing an exemplary compound signal formed by a first optical signal at a high frequency and a second optical signal at a low frequency, in accordance with one or more embodiments of the present invention.

(3) FIG. 3 is a table showing an exemplary control signal relationship for switching the function and/or mode of the optical signal in accordance with one or more embodiments of the present invention.

DETAILED DESCRIPTION

(4) Reference will now be made in detail to various embodiments of the invention, examples of which are illustrated in the accompanying drawings. 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 of the present invention, 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 disclosure.

(5) Some portions of the detailed descriptions which follow are presented in terms of processes, procedures, logic, functions, and other symbolic representations of operations on signals, code, data bits, or data streams within a computer, transceiver, processor, controller and/or memory. These descriptions and representations are generally used by those skilled in the data processing arts to effectively convey the substance of their work to others skilled in the art. A process, procedure, logic operation, function, process, etc., is herein, and is generally, considered to be a step or a self-consistent sequence of steps or instructions leading to a desired and/or expected result. The steps generally include physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical, magnetic, optical, or quantum signals capable of being stored, transferred, combined, compared, and/or otherwise manipulated in a computer, data processing system, optical component, or circuit. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, streams, values, elements, symbols, characters, terms, numbers, information or the like. It should be borne in mind, however, that all of these and similar terms are associated with the appropriate physical quantities and/or signals, and are merely convenient labels applied to these quantities and/or signals.

(6) Unless specifically stated otherwise, or as will be apparent from the following discussions, it is appreciated that throughout the present application, discussions utilizing terms such as processing, operating, calculating, determining, or the like, refer to the action and processes of a computer, data processing system, or similar processing device (e.g., an electrical, optical, or quantum computing or processing device or circuit) that manipulates and transforms data represented as physical (e.g., electronic) quantities. The terms refer to actions and processes of the processing devices that manipulate or transform physical quantities within the component(s) of a circuit, system or architecture (e.g., registers, memories, other such information storage, transmission or display devices, etc.) into other data or information similarly represented as physical quantities within other components of the same or a different system or architecture.

(7) Furthermore, in the context of this application, the terms signal and optical signal refer to any known structure, construction, arrangement, technique, method and/or process for physically transferring a signal or optical signal, respectively, from one point to another. Also, unless indicated otherwise from the context of its use herein, the terms fixed, given, certain and predetermined generally refer to a value, quantity, parameter, constraint, condition, state, process, procedure, method, practice, or combination thereof that is, in theory, variable, but is typically set in advance and not varied thereafter when in use. Similarly, for convenience and simplicity, the terms time, rate, period and frequency are, in general, interchangeable and may be used interchangeably herein, as are the terms data, bits, and information, but these terms are generally given their art-recognized meanings.

(8) For the sake of convenience and simplicity, the terms optical and optoelectronic are generally used interchangeably herein, and use of either of these terms also includes the other, unless the context clearly indicates otherwise, but these terms are generally given their art-recognized meanings herein. Furthermore, the term transceiver refers to a device having at least one receiver and at least one transmitter, and use of the term transceiver also includes the individual terms receiver and/or transmitter, unless the context clearly indicates otherwise. Also, for convenience and simplicity, the terms connected to, coupled with, communicating with, coupled to, and grammatical variations thereof (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) may be used interchangeably, but these terms are also generally given their art-recognized meanings.

(9) Various embodiments and/or examples disclosed herein may be combined with other embodiments and/or examples, as long as such a combination is not explicitly disclosed herein as being unfavorable, undesirable or disadvantageous. The invention, in its various aspects, will be explained in greater detail below with regard to exemplary embodiments.

An Exemplary Circuit and Transmitter

(10) As shown in FIG. 1, a multifunctional laser driving circuit 100 includes a signal transmitter module (e.g., TOSA) 130, a controller (e.g., MCU) 140, a first laser driver 120, and a second laser driver 125. The signal transmitter module 130 is electrically connected with the controller 140, the first laser driver 120 and the second laser driver 125, and the controller 140 is further electrically connected with the first laser driver 120 and the second laser driver 125. The signal transmitter module 130 is electrically connected with the controller 140 via a bidirectional bus 115, which may be a two-wire inter-integrated circuit (IIC or I2C) bus. The first laser driver 120 and the second laser driver 125 drive the laser diode (LD) 135 in the signal transmitter module 130 over a unidirectional (one-way) bus 122. The bus 122 may carry a differential signal from each of the first laser driver 120 and the second laser driver 125. For example, the first laser driver 120 may send a data signal on bus 122, and the second laser driver 125 may send a line monitoring or line detection signal on bus 122. The bus 122 may also carry single-ended signals from the first and second laser drivers 120 and 125. The controller 140 is electrically connected with the first laser driver 120 via a bidirectional control and feedback bus 142a and a unidirectional enable/disable bus 144a. The enable/disable signal on the bus 144a may be a simple, one-bit digital signal. The controller 140 is electrically connected with the second laser driver 125 via a bidirectional control and feedback bus 142b and a unidirectional enable/disable bus 144b. The buses 142b and 144b and the control, feedback and enable/disable signals thereon may be functional and/or structural duplicates of the buses 142a and 144a and the control, feedback and enable/disable signals thereon.

(11) The laser driving circuit 100 also includes an electrical interface 110, which transfers signals between the laser driving circuit 100 and an external device (e.g., a host device, such as an optical network terminal or an optical network unit, in an optical network). The interface 110 communicates with the MCU 140 and the TOSA 130 (e.g., via data signals and/or instructions) over the bidirectional bus 115. The interface 110 also sends an enable signal (e.g., a transmitter enable/disable signal) to the MCU 140. The interface 110 sends a first electrical signal (e.g., an electrical data signal) to the first laser driver 120 on bus 112 and a second electrical signal (e.g., an electrical line monitoring signal) to the second laser driver 125 on bus 114. The buses 112 and 114 may be differential (as shown) or single-ended.

(12) The first and second laser drivers 120 and 125 are configured to drive the laser diode 135, which converts a first electrical signal from the first laser driver 120 into a first optical signal and a second electrical signal from the second laser driver 125 into a second optical signal (e.g., for transmission over an optical fiber or other optical transmission medium). The first optical signal and the second optical signal may be combined into a compound signal (e.g., for transmission over the optical fiber). In various embodiments, the electrical signals (e.g., on bus 122) corresponding to the first optical signal and the second optical signal may be synchronized and logically combined to form the compound signal. For example, the electrical signals corresponding to the first optical signal and the second optical signal may be stored in separate latches (not shown, but which may be at the output terminals of the first and second laser drivers 120 and 125) receiving the same timing signal, then passed through a logic gate, such as an AND gate (although other logic gates that combine the electrical signals in a manner in which the first optical signal and the second optical signal can be recovered at the receiving end of the optical transmission medium are contemplated).

(13) When the first laser driver 120 is enabled and the second laser driver 125 is disabled, only the first laser driver 120 drives the laser diode 135, which outputs a first optical signal (e.g., Data in FIG. 2). The first optical signal Data has a first, relatively high frequency. When the second laser driver 125 is enabled and the first laser driver 120 is disabled, only the second laser driver 125 drives the laser diode 135, which outputs a second optical signal (e.g., Monitor in FIG. 2). The second optical signal Monitor has a second, relatively low frequency. For example, the first frequency may be from 1 MHz to 1 THz (e.g., 10 MHz to 1000 MHz, or any value or range of values therein), and the second frequency may be from 1 kHz to 1 GHz (e.g., 100 kHz to 100 MHz, or any value or range of values therein), but the first frequency is always greater than the second frequency in such embodiments, for example by a factor of at least 5, 10, 20, 30, or any other number greater than 5.

(14) In addition, the first optical signal may have a first, relatively high amplitude (e.g., power), and the second optical signal may have a second, relatively low amplitude (or power). For example, the second amplitude or power may be 5-50% of the first amplitude or power (e.g., 10-20%, or any other value or range of values therein).

(15) When both the first laser driver 120 and the second laser driver 125 are enabled, both the first laser driver 120 and the second laser driver 125 drive the laser diode 135, which outputs a combined optical signal (e.g., Compound in FIG. 2). A device at the receiving end of the optical fiber (not shown) can relatively easily recover or extract the second optical signal by determining the average optical power of the received signal (e.g., Compound in FIG. 2).

(16) However, when the network indicates that there is a fault in optical signal transmission (e.g., the device at the receiving end of the fiber does not receive the optical signal when it expects to receive the optical signal), or the network or a user (e.g., the host) otherwise instructs the laser driving circuit 100 to detect faults or breaks in the optical fiber, the second laser driver 125 is enabled and the first laser driver 120 is disabled, and the second laser driver 125 drives the laser diode 135 to output an alternative second optical signal (e.g., Detect in FIG. 2). The alternative second optical signal may have some or all of the same characteristics (e.g., frequency and power) as the second optical signal, but it has a function different from the second optical signal. For example, the alternative second optical signal may determine a number and/or location of faults or breaks in the fiber from the reflections of the alternative second optical signal (e.g., from a number of predetermined positions or locations in the fiber). The reflections are detected by optical signal receiving hardware (e.g., a photodiode and one or more amplifiers, such as a transimpedance amplifier [TIA]) elsewhere in the optical module (e.g., transceiver) containing the laser driving circuit 100. Alternatively, to improve the detection of the reflected optical signal, the optical output power of the alternative second optical signal can be increased relative to the second optical signal (e.g., by 2, 5, 10, 20, or any other value greater than 2). In one example, the optical output power of the alternative second optical signal is the maximum output power permitted for the laser diode under the operating conditions of the laser driving circuit 100. In another example, the optical output power of the alternative second optical signal is about the same as the first optical signal.

(17) Control instructions for signal function switching and/or signal transmission modes may be stored in a register in the controller 140. For example, FIG. 3 shows a truth table for the signal function switching and/or signal transmission modes of the laser driving circuit 100.

(18) For example, when the transmitter disable signal Tx_disable 116 is active (e.g., has a logic high or binary 1 state), the first and second laser drivers 120 and 125 and the signal transmitter 130 are inactive (or powered down). As a result, the optical signal (if any) output by the signal transmitter 130 has a power or strength of substantially zero (e.g., <45 dBm). However, when the transmitter disable signal Tx_disable 116 is inactive (e.g., has a logic low or binary 0 state), the first and second laser drivers 120 and 125 and the signal transmitter 130 are active (or powered up), and the laser driving circuit 100 can switch among the various optical signal functions and/or enter the various operational modes.

(19) For example, when the line detection (or line monitor) enable signal 142b is active (e.g., has a logic high or binary 1 state) and the data enable signal 142a is inactive (e.g., has a logic low or binary 0 state), the second laser driver 125 is active and the first laser driver 120 is inactive. The laser driving circuit 100 then enters a line detection mode, and can perform an OTDR function as described herein. As described earlier, the amplitude of the optical signal in the line detection mode may be the same as the optical data signal or the maximum output power possible for an optical signal generated by the laser diode 135.

(20) In addition, when the line detection (or line monitor) enable signal 142b is inactive (e.g., has a logic low or binary 0 state) and the data enable signal 142a is active (e.g., has a logic high or binary 1 state), the first laser driver 120 is active and the second laser driver 125 is inactive. The laser driving circuit 100 then enters a data communication mode, and can transmit an optical data signal as described herein.

(21) Furthermore, when both the line detection (or line monitor) enable signal 142b and the data enable signal 142a are active (e.g., have a logic high or binary 1 state), both the first laser driver 120 and the second laser driver 125 are active. The laser driving circuit 100 then enters a combined function mode, and transmits a compound optical signal (including both the optical data signal and an optical line monitoring signal) as described herein. In this mode, the optical line monitoring signal may have an amplitude that is less than half of that of the optical data signal (and in one example, about 20% of the amplitude of the optical data signal), resulting in the compound signal having a modulation depth of <50% and in the one example, about 20%). The amplitude of both the optical data signal and the optical line monitoring signal can be modified, adjusted or changed to provide the compound signal with a desired or predetermined modulation depth.

An Exemplary Method of Transmitting a Compound Optical Signal

(22) One aspect of the present invention involves a method of driving a laser, forming a multi-functional or compound optical signal, and/or transmitting the same over an optical fiber. In the present invention, two signals with different functions are combined into one compound signal and then transmitted over one optical communication line (e.g., optical fiber).

(23) The method includes enabling or disabling driving the laser using first and second electrical signals, generating a first optical signal when the first electrical signal enables driving the laser, generating a second optical signal when the second electrical signal enables driving the laser, combining the first optical signal and the second optical signal into a compound signal, and outputting the first optical signal, the second optical signal, and the compound signal over an optical transmission medium. The compound signal may be generated when both the first electrical signal and the second electrical signal enable driving the laser. For example, the first optical signal may be transmitted when a first laser driver is enabled and a second laser driver is disabled, the second optical signal may be transmitted when the first laser driver is disabled and the second laser driver is enabled, and the combined signal may be transmitted when the first laser driver and the second laser driver are enabled.

(24) The first optical signal may have a first frequency, and the second optical signal may have a second frequency significantly less than the first frequency, as described herein. Furthermore, the first optical signal may be a data signal, the second optical signal may be a line monitoring signal or a line detection signal, and the second optical signal may be the line detection signal when the optical transmission medium does not work properly, or a user or a network comprising the optical transmission medium instructs a transmitter comprising the laser to detect faults in the optical transmission medium. Thus, the method may further comprise driving the laser diode with the first laser driver according to an electrical data signal, and driving the laser diode with the second laser driver according to an electrical line monitoring signal. In general, the first and second laser drivers are enabled or disabled with a controller.

(25) Additionally or alternatively, the method may further comprise recovering the second optical signal by detecting an average optical power of the second optical signal. Also, the method may further comprise regulating a frequency of the line detection signal to increase an accuracy of detecting the faults in the optical transmission medium, as described herein (e.g., by increasing an output strength, output power or amplitude of the line detection signal). In one example, increasing the output strength of the line detection signal comprises increasing an output power of the second laser driver.

CONCLUSION/SUMMARY

(26) Embodiments of the present invention advantageously provide a multifunctional laser driving circuit and method of using the same. The laser driving circuit includes a first laser driver, a second laser driver, and a controller that enables or disables the first and second laser drivers to switch among the laser output modes or functions (e.g., data, line monitoring, combined data and line monitoring functions, or line detection). The multifunctional laser driving circuit and method can be implemented using conventional equipment, and offers a simple, low cost way to test for or detect breaks or faults in optical fibers. The present multifunctional laser driving circuit and method are applicable to optical devices, optical modules and optical communication devices.

(27) 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 teachings. 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.