KR20120133159A - Apparatus and Method for Controlling Current in Optical Transmitter - Google Patents

Apparatus and Method for Controlling Current in Optical Transmitter Download PDF

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Publication number
KR20120133159A
KR20120133159A KR1020110051688A KR20110051688A KR20120133159A KR 20120133159 A KR20120133159 A KR 20120133159A KR 1020110051688 A KR1020110051688 A KR 1020110051688A KR 20110051688 A KR20110051688 A KR 20110051688A KR 20120133159 A KR20120133159 A KR 20120133159A
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South Korea
Prior art keywords
current
control signal
current control
bias current
modulation
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KR1020110051688A
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Korean (ko)
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이종훈
조승현
이지현
이한협
이은구
이상수
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한국전자통신연구원
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Publication of KR20120133159A publication Critical patent/KR20120133159A/en

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    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current
    • G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
    • G05F1/462—Regulating voltage or current wherein the variable actually regulated by the final control device is dc as a function of the requirements of the load, e.g. delay, temperature, specific voltage/current characteristic
    • G05F1/463—Sources providing an output which depends on temperature
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/10—Regulating voltage or current
    • G05F1/46—Regulating voltage or current wherein the variable actually regulated by the final control device is dc
    • G05F1/56—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices
    • G05F1/565—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor
    • G05F1/567—Regulating voltage or current wherein the variable actually regulated by the final control device is dc using semiconductor devices in series with the load as final control devices sensing a condition of the system or its load in addition to means responsive to deviations in the output of the system, e.g. current, voltage, power factor for temperature compensation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/0683—Stabilisation of laser output parameters by monitoring the optical output parameters

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Optics & Photonics (AREA)
  • Semiconductor Lasers (AREA)

Abstract

PURPOSE: A current control device and method of an optical transmitter are provided to maximize energy efficiency by assuring uncooled operation of a light source. CONSTITUTION: A temperature reference control signal generator(330) generates a current control signal according to temperature variation in a light source. A current controller generates a variable current according to the current control signal. The current control signal includes a bias current control signal and a modulation current control signal. The current controller includes a bias current controller(310) and a modulation current controller(320). [Reference numerals] (310) Bias current controller; (311) Variable bias current generator; (312) Bias current corrector; (320) Modulation current controller; (321) Variable modulation current generator; (322) Modulation current corrector; (330) Temperature reference control signal generator; (331) Temperature change detector; (332) Bias current control signal generator; (333) Modulation current control signal generator

Description

Apparatus and Method for Controlling Current in Optical Transmitter

TECHNICAL FIELD The present invention relates to an optical communication system, and more particularly, to an apparatus and method for controlling a bias current and a modulation current of an optical transmitter.

Recently, there is an active discussion on green IT technologies that improve energy efficiency. The term Green was originally a term that began in a specific field, such as simply Green Computing, but has been used throughout the industry in recent years. Not only eco-friendly technology but also the whole technology that enables convergence greening is collectively referred to. This technology development paradigm is widely applied in the network field.

Accordingly, various approaches for greening are taking place across modules and systems in optical networks or optical subscriber networks. For example, in order to reduce the power consumption of the optical transmitter, not only the effort to reduce the power consumption of the transmitter itself in the physical layer but also to control operation over time such as a sleep mode or to maximize energy efficiency in the upper layer. Various efforts are underway.

WDM-passive optical network (WDM-PON) technology using wavelength division multiplexing using Reflective Semiconductor Optical Amplifeir (RSOA), which is a kind of optical network, is easy to manage inventory and simplify network structure. It's easy to manage. In the WDM-PON, the wavelength division multiplexing method is used for communication between a central office (CO) or an optical line terminal (OLT) and a subscriber by using a wavelength specified for each subscriber. In this way, it is possible to provide independent and large capacity communication service for each subscriber, and has excellent security. Unlike the time division multiple access (TDMA) method, the modulation and demodulation of the light source is for one subscriber only. As a result, it is possible to use a light source with a low modulation rate and output and a receiver with a narrow bandwidth.

However, OLT-ONU structure is composed of 1: N in TDM-PON, whereas N: N is constructed in WDM-PON, which increases the system construction cost. In addition, the company is inferior in price competitiveness to TDM-PON so far due to limited market commercialization. A viable solution for price competitive WDM-PON applications is the implementation of an optical transceiver with a colorless light source that guarantees uncooled operation.

The TEC (Thermo-Electric Color) included in the light source accounts for approximately 30% to 50% of the cost of the light source. Developing an optical transceiver with uncooled operation can reduce the cost of the optical transceiver, so it is very important to reduce the cost of system construction. Play a role. In addition, the TEC driving power for the optical transmitter, especially the cooled operation, takes up a large portion of the total power consumption of the colorless optical transceiver. Therefore, it is very important to develop an optical transceiver capable of uncooled operation for greening the network in the future.

Reflective semiconductor optical amplifiers (RSOAs) are divided into bulk, quantum wells, and quantum dots according to the structure of the gain medium. Gain media such as quantum dots have little characteristic variation over temperature, making them ideal for uncooled operation but failing to provide sufficient performance and cost for commercialization. Quantum Well can provide better temperature characteristics than bulk, but its use is limited due to its polarization characteristics. In the case of bulk type RSOA, the cooled RSOA optical transmitter has been commercialized and applied in the field due to its excellent gain characteristics and low polarization dependency.

In order to realize a realistic Uncooled RSOA optical transmitter, Bulk RSOA should be used to guarantee uncooled operation. The variation of the slope efficiency and threshold current of Bulk RSOA is very large compared to that of DFB or FP-LD light source.

Particularly, in wavelength recycling WDM-PON, the extinction ratio (ER) of the downlink signal must be kept constant for remodulation of the uplink signal. The conventional bias and modulation current control method maintains a constant extinction ratio in a light source having such a large variability. Inadequate to maintain. In addition, since the conventional bias and modulation current control schemes are optimized for the operation of DFB or FP-LD light sources, the implementation of an uncooled optical transmitter using a light source such as RSOA with a large temperature fluctuation rate requires a more effective bias and modulation current control scheme.

The present invention is directed to an apparatus and method for controlling current in an optical transmitter that ensures uncooled operation of a light source to maximize energy efficiency.

The present invention is a current control device of the optical transmitter, a temperature reference current control signal generator for generating and outputting a bias current control signal and a modulation current control signal according to the temperature variation of the light source, and outputs from the temperature reference current control signal generator A bias current controller for generating a variable bias current according to the bias current control signal generated and correcting the generated variable bias current according to an output value of a light source, and a variable current control signal output from the temperature reference current control signal generator; And a modulation current controller for generating a modulation current and correcting the generated variable modulation current according to the bias value corrected by the bias current controller.

The present invention provides a method for accurately controlling a current applied to a light source by a current control device of an optical transmitter, the method comprising: detecting a temperature variation of a light source, generating a variable bias current and a variable modulation current according to the temperature variation; Monitoring the output of the light source, correcting the variable bias current such that the output of the light source is constant according to the monitored light source output, and correcting the variable modulation current such that the extinction ratio is constant according to the variable bias current correction value. Include.

The present invention provides a current control device and method for ensuring an uncooled operation for a light source having a high variation in temperature in an optical transmitter, thereby reducing power consumption of the optical transmitter and contributing to greening the network and reducing the overall optical transceiver implementation cost. The system construction cost can be reduced.

1 is a configuration diagram of a current control device of a general optical transmitter.
2A is a graph for explaining general bias current control.
2B is a graph for explaining general modulation current control.
3 is a block diagram of an apparatus for controlling current of an optical transmitter according to a preferred embodiment of the present invention.
4A is a graph for describing bias current control according to an exemplary embodiment of the present invention.
4B is a graph for explaining modulation current control according to an exemplary embodiment of the present invention.
5 is a flowchart illustrating a bias modulation current control method according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

In the following description of the present invention, when it is determined that detailed descriptions of related known functions or configurations may unnecessarily obscure the gist of the embodiments of the present invention, the detailed description thereof will be omitted.

Terms used throughout the specification are terms defined in consideration of functions in the embodiments of the present invention, and may be sufficiently modified according to the intention, custom, etc. of the user or operator, and the definitions of these terms are used throughout the specification of the present invention. It should be made based on the contents.

1 is a configuration diagram of a current control device of a general optical transmitter.

Referring to FIG. 1, a general optical transmitter includes a bias current controller 110 and a modulation current controller 120.

The bias current controller 110 basically provides an automatic power control (APC) function to maintain an optical output having a constant fixed power regardless of a change in operating temperature. The bias current controller 110 includes a bias current generator 111 and a bias current corrector 112.

An operation of the bias current controller 110 will be described with reference to FIG. 2A.

2A is a graph illustrating a general bias current controller.

The bias current generator 111 generates and outputs a constant bias current 211 as shown in FIG. 2A. Then, the bias current corrector 112 monitors the change in the light source power according to the temperature change, and corrects the fixed bias current 211 generated by the bias current generator 111 according to the monitored change value. . That is, in order to make the output power of the light source constant, the bias current correcting unit 112 changes the output power of the light source as shown in FIG. 2A at the fixed bias current 211.

Figure pat00001
Bias current increased or decreased by (212)
Figure pat00002
213 to be corrected. In more detail, the bias current corrector 112 increases the bias current when the light output decreases, and decreases the bias current when the light output increases to automatically control the light output for temperature changes.

On the other hand, the semiconductor light source decreases the efficiency as the operating temperature increases, and as a result, the threshold current and the slope efficiency decrease. If the gradient efficiency variation with temperature is small and predictable, the reference modulation current can be increased or decreased in proportion to the bias current change to maintain a constant extinction ratio to compensate for the optical extinction ratio variation.

Referring to FIG. 1, the modulation current controller 120 includes a modulation current generator 121 and a modulation current corrector 122 in detail to maintain a constant extinction ratio. The detailed operation of the modulation current controller 120 will be described with reference to FIG. 2B.

2B is a graph for explaining general modulation current control.

The modulation current generator 121 generates and outputs a constant modulation current 221 as shown in FIG. 2B. Then, the modulation current corrector 122 outputs the fixed modulation current 221 output from the modulation current generator 121 according to the bias current correction signal transmitted from the bias current controller 110.

Figure pat00003
Modulation current increased or decreased by (222)
Figure pat00004
223 to be corrected. The operation of the modulation current corrector 122 may be expressed as Equation 1 below.

Figure pat00005

Meaning the initial value of the modulation current applied to the RSOA in Equation 1

Figure pat00006
Is the fixed modulation current 221, and means the initial value of the bias current applied to the RSOA.
Figure pat00007
Is a bias current control signal transmitted from the bias current controller 110, K may be expressed as Equation 2 below.

Figure pat00008

The modulation current controller 120 indirectly compensates for the extinction ratio variation with respect to the change in operating temperature without the complexity of the extinction ratio detection or the peak detection circuit configuration. That is, since it is not a feedback control like the APC loop, it is necessary to set an appropriate K value according to the type of light source and the type of sample.

In addition, as a method to have a constant extinction ratio irrespective of temperature change, a method of compensating a gradient efficiency variation value at a corresponding temperature through temperature detection is set in advance by setting a predictable gradient efficiency variation value according to the temperature. .

However, when the aforementioned methods are applied to a light source such as RSOA having a large characteristic variation with temperature, it is difficult to achieve uniformity of characteristics. For example, in the case of extinction ratio control, the variability in the operating temperature range is large, and linear compensation, which compensates in the first order proportional to the existing temperature, makes it difficult to achieve characteristic uniformity over the entire operating temperature. In particular, abrupt declines in efficiency at high temperatures require more than one order of nonlinear compensation. The term 'linear compensation of first-order proportion' used above refers to a sufficient linearizable compensation in a first-order equation where the relationship between the bias current and the modulation current is represented by a constant K. Otherwise, it is referred to as nonlinear compensation. .

As another example, a lookup method, that is, a table of modulation currents according to a temperature, and a method of searching and setting the modulation current at each temperature may be possible. However, this method varies greatly depending on RSOA sample variation and heat dissipation condition variation, and it is difficult to compensate for the deterioration of characteristics over time.

The present invention proposes a bias current and modulation current control apparatus and method for guaranteeing the characteristics of an optical signal when an uncooled operation of a light source having a large characteristic variation according to temperature is performed. An exemplary embodiment of the present invention relates to a bias current and modulation current control apparatus and method for guaranteeing uncooled operation for an RSOA, particularly an RSOA having a bulk structure of a gain medium.

3 is a block diagram of an apparatus for controlling current of an optical transmitter according to a preferred embodiment of the present invention.

Referring to FIG. 3, an apparatus for controlling current of an optical transmitter according to an exemplary embodiment of the present invention includes a bias current controller 310, a modulation current controller 320, and a temperature reference current control signal generator 330.

According to a preferred embodiment of the present invention, the temperature reference current control signal generator 330 generates a bias current and a modulation current control signal according to a temperature change. For this, the temperature variation detection unit 331 and the bias current control signal are described. The generator 332 and the modulation current control signal generator 333 are included.

The bias current controller 310 basically provides an automatic power control (APC) function to maintain a light output having a constant fixed power regardless of a change in operating temperature of the light source. In detail, the current controller 310 includes a variable bias current generator 311 and a bias current corrector 312.

An operation of the bias current controller 310 will be described with reference to FIG. 4A.

4A is a graph for describing bias current control according to an exemplary embodiment of the present invention.

Unlike the prior art, the variable bias current generator 311 generates and outputs a variable bias current 411 as shown in FIG. 4A according to a control signal transmitted from the temperature reference current generator 330. Then, the bias current corrector 312 monitors the change in the light source power, and corrects the variable bias current 411 generated by the variable bias current generator 311 in more detail according to the monitoring value. That is, in order to make the output power of the light source constant, the bias current corrector 312 may change the output power of the light source according to the variation in the output power of the light source as shown in FIG. 4A in the variable bias current 411.

Figure pat00009
Bias current increased or decreased by 412 (
Figure pat00010
(413). In more detail, the bias current corrector 312 automatically increases the bias current when the light output decreases, and decreases the bias current when the light output increases to automatically control the light output for temperature changes.

Referring back to FIG. 3, the modulation current controller 320 includes a variable modulation current generator 321 and a modulation current corrector 322 in detail to maintain a constant extinction ratio. The detailed operation of the modulation current controller 320 will be described with reference to FIG. 4B.

4B is a graph for explaining modulation current control according to an exemplary embodiment of the present invention.

The variable modulation current generator 321 generates and outputs a modulation current 421 that is variable according to temperature as shown in FIG. 4B according to a control signal output from the temperature reference current control signal generator 330. Then, the modulation current corrector 322 receives the variable modulation current 421 output from the modulation current generator 321 according to the bias current correction signal transmitted from the bias current controller 310.

Figure pat00011
Modulation current increased or decreased by (422)
Figure pat00012
423). The operation of the variable modulation current corrector 422 may be expressed as Equation 3 below.

Figure pat00013

In Equation (1)

Figure pat00014
Is the variable modulation current 421 according to the temperature,
Figure pat00015
Is a bias current control signal transmitted from the bias current controller 310, K (T) can be expressed as shown in Equation 4 below.

Figure pat00016

The modulation current controller 320 compensates for the extinction ratio fluctuations due to the change in operating temperature indirectly without the complexity of the extinction ratio detection or the peak detection circuit configuration. This method is to reduce the level of variability greatly by setting the temperature reference bias current variably according to temperature even for a light source having a large variability. As with bias current control, a temperature-based modulation current is generated to minimize the rate of modulation current variation. The temperature-based modulation current that varies with temperature minimizes fluctuations in gradient efficiency with temperature and consequently enables predictable, that is, linear linearization.

5 is a flowchart illustrating a current control method in an optical transmitter according to a preferred embodiment of the present invention.

Referring to FIG. 5, in operation 510, the current control device of the optical transmitter detects a temperature variation of a light source. In operation 520, a bias current and a modulation current according to the temperature change are generated.

Next, the current control device monitors the output of the light source in step 530 and corrects the variable bias current according to the monitored light source output in step 540. That is, in order to make the output power of the light source constant, the current control apparatus changes the output power of the light source according to the variation of the output power of the light source as shown in FIG. 4A in the variable bias current 411.

Figure pat00017
Bias current increased or decreased by 412 (
Figure pat00018
(413). In more detail, the current control device automatically increases the bias current when the light output decreases, and decreases the bias current when the light output increases to automatically control the light output for temperature changes.

Referring back to FIG. 5, in operation 550, the current controller corrects the variable modulation current according to the variable bias current correction value. That is, the current control device sets the variable modulation current 421 as shown in FIG. 4B according to the bias current correction value.

Figure pat00019
Modulation current increased or decreased by (422)
Figure pat00020
423). Such variable modulation current correction may be expressed as in Equation 3 above.

The method proposed in the present invention described above features and applies a more general K (T) to the existing K modulation control method which maintains a constant extinction ratio. These applications are also achieved within the first linearization range to simplify circuit design and modification. As a result, the proposed method can guarantee the uncooled operation of the highly volatile light source by using the existing commercial LDD, that is, the LDD designed for the light source having low variability, without any change.

Claims (12)

A temperature reference current control signal generation unit generating and outputting a current control signal according to a temperature variation of the light source;
And a current controller configured to generate a variable current according to the current control signal output from the temperature reference current control signal generator.
The method of claim 1,
The current control signal includes a bias current control signal and a modulation current control signal,
The current controller
A bias current controller configured to generate a variable bias current according to the current control signal output from the temperature reference current control signal generator;
And a modulation current controller configured to generate a variable modulation current according to the current control signal output from the temperature reference current control signal generator.
The method of claim 2, wherein the bias current control unit
The current control device of the optical transmitter, characterized in that for correcting the variable bias current generated so that the output of the light source is constant.
The method of claim 3, wherein the modulation current control unit
The current control device of the optical transmitter for correcting the generated variable modulation current according to the bias current value corrected by the bias current controller.
The method of claim 1, wherein the temperature reference current control signal generator
A temperature fluctuation detector for detecting a temperature fluctuation of the light source,
A bias current control signal generation unit which generates and outputs a bias current control signal according to the temperature variation detection value output from the temperature variation detection unit;
And a modulation current control signal generation unit for generating and outputting a modulation current control signal according to the temperature variation detection value output from the temperature variation detection unit.
The method of claim 2, wherein the bias current control unit
A variable bias current generator for generating a bias current that varies with temperature fluctuation according to a bias current control signal output from the temperature reference current control signal generator;
And a bias current corrector for monitoring the power of the light source and correcting the variable bias current generated by the variable bias current generator so that the output power of the light source is constant according to the monitored value. Device.
The method of claim 2, wherein the modulation current corrector
A variable modulation current generator for generating a modulation current that varies according to a temperature according to a control signal output from the temperature reference current control signal generator;
And a modulation current corrector for correcting the variable modulation current output from the variable modulation current generator according to the bias current correction signal transmitted from the bias current controller.
The method of claim 7, wherein the modulation current corrector
Optical transmitter current control device characterized in that for correcting the modulation current through the following equation (5).
<Equation 5>
Figure pat00021

In Equation 5 above
Figure pat00022
Is the variable modulation current with temperature,
Figure pat00023
Is a bias current control signal transmitted from the bias current controller, and K (T) is expressed as in Equation 6 below.
&Quot; (6) &quot;
Figure pat00024

 In the method for controlling the current applied to the light source by the current control device of the optical transmitter,
Detecting a temperature variation of the light source,
Generating a current according to the temperature change.
The method of claim 9, wherein the generating step
A current control method of an optical transmitter, characterized by generating a variable bias current and a variable modulation current.
The method of claim 8,
Monitoring the output of the light source,
And correcting the variable bias current such that the output of the light source is constant in accordance with the monitored light source output.
The method of claim 8,
And correcting the variable modulation current such that the extinction ratio is constant according to the variable bias current correction value.
KR1020110051688A 2011-05-30 2011-05-30 Apparatus and Method for Controlling Current in Optical Transmitter KR20120133159A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20160107029A (en) 2015-03-03 2016-09-13 한국전자통신연구원 Apparatus and method for optimizing bias of laser diode in analog optical signal transmission
US10659167B1 (en) 2018-12-14 2020-05-19 Optomind Inc. Active optical cable
KR20200074822A (en) * 2018-12-14 2020-06-25 (주)옵토마인드 Active Optical Cable

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20160107029A (en) 2015-03-03 2016-09-13 한국전자통신연구원 Apparatus and method for optimizing bias of laser diode in analog optical signal transmission
US10659167B1 (en) 2018-12-14 2020-05-19 Optomind Inc. Active optical cable
WO2020122491A1 (en) * 2018-12-14 2020-06-18 (주)옵토마인드 Active optical cable
KR20200074822A (en) * 2018-12-14 2020-06-25 (주)옵토마인드 Active Optical Cable
US11012158B2 (en) 2018-12-14 2021-05-18 Optomind Inc. Active optical cable

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