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WO2007069045A1 - Émetteur/récepteur de données optique économique - Google Patents

Émetteur/récepteur de données optique économique Download PDF

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Publication number
WO2007069045A1
WO2007069045A1 PCT/IB2006/003593 IB2006003593W WO2007069045A1 WO 2007069045 A1 WO2007069045 A1 WO 2007069045A1 IB 2006003593 W IB2006003593 W IB 2006003593W WO 2007069045 A1 WO2007069045 A1 WO 2007069045A1
Authority
WO
WIPO (PCT)
Prior art keywords
light emitting
data transceiver
optical data
emitting means
optical
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/IB2006/003593
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English (en)
Inventor
Piet De Pauw
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Melexis NV
Original Assignee
Melexis NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Melexis NV filed Critical Melexis NV
Publication of WO2007069045A1 publication Critical patent/WO2007069045A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/50—Transmitters
    • H04B10/564—Power control

Definitions

  • the invention relates to optical data transceivers and in particular to optical data transceivers having means for monitoring and controlling output power levels.
  • Optical data transmission systems use light to carry digital data along fibre optic cables.
  • the light is generated by a first transceiver, coupled to the fibre, and travels along the fibre to its far end whereupon it is incident upon a second transceiver.
  • the first transceiver acts to convert electrical signals into optical signals and the second transceiver acts to convert the optical signals back into electrical signals. This process may of course be reversed, with signals being sent from the second transceiver to the first transceiver, if desired.
  • Each transceiver has an optically active element or elements.
  • the optically active elements are a light emitting means and a light sensing means. It is however possible, if data transmission is required in a single direction only, that transceivers may be adapted only to emit light or to sense light i.e. to have a single optically active element being either a light emitting means or a light sensing means as appropriate. In this application, the term transceiver is used to encompass all three possibilities.
  • optical transceivers are housed in a protective package, said protective package having an aperture through which light may pass between the optically active elements of the transceiver and the exterior of the package and the
  • the aperture is adapted such that an optical fibre may be inserted and releaseably retained.
  • the optical fibre is conventionally terminated in a ferrule.
  • the aperture is adapted to have a cross-section which corresponds to the cross-section of the ferrule. If the ferrule is not aligned correctly with the optically active elements, coupling between the optical fibre and the optical data transceiver is reduced and thus a proportion of the signal is lost. These losses reduce the effective intensity of the transmitted data signals and hence reduce the efficiency, the sensitivity, data rate, Bit Error Rate, and maximum communication range of the signal from their optimum values.
  • Power output in an optical data transceiver also typically varies with temperature.
  • a number of schemes have been proposed for monitoring the power output of a transceiver to ensure that power levels remain below permitted limits.
  • One such scheme is to use a dedicated light sensing means (typically, a photodiode) to monitor the intensity of light transmitted by the light emitting means. This can be done directly or by reflection from a target. Whilst this scheme does solve the problem, it adds to the cost and complexity of the data transceivers. Accordingly, such a solution is not suitable in low cost applications.
  • the light emitting means is a laser diode
  • the laser diode would be operated with a steady bias current onto which the signalling current is superimposed.
  • the signalling current switches the laser above and below the threshold current such as to modulate the laser optical output.
  • I ⁇ bias current
  • I t hre s hoi ⁇ there is an import turn-on delay of the laser, which gives rise to pulse width distortion of the laser diode light pulse, known as average pulse width distortion.
  • the average pulse width distortion increases with the square of the difference between I b i as and Ifeeshoid-
  • the bias current In order to minimise this distortion and thus improve data transmission, one can set the bias current to be higher than the laser threshold current. This minimises pulse width distortion but has the disadvantage that in order to maintain the same modulation depth (typically expressed as the log base 10 of the ratio of the optical power in a logic '1' to the optical power in a logic '0'), the modulation current of the laser must be larger compared to the basic case. Accordingly, this implies higher values of the average laser power.
  • a third possibility is to modify the bias current with temperature. This can enable the power output to be maintained at close to a desired level even when the temperature of the light emitting means varies.
  • the MAX3905 150 Mbps Automotive VCSEL driver of Maxim Integrated Products, USA shows a linear variation of the VCSEL bias current.
  • Such a system may typically have an extinction ratio 6 (equivalent to modulation depth). Whilst this does provide some benefits, it does not directly map onto variations in the VCSEL threshold current over the specified temperature range and so some unwanted variation of power output still occurs.
  • an optical data transceiver comprising: a light emitting means operable to emit light in response to received electrical current; a processing means for controlling electrical signals input to said light emitting means; and a means for determining the bit error rate of light signals emitted by the light emitting means and passing a signal indicative thereof to the processing means wherein the processing means is operable to maintain a desired output power level from the light emitting means by varying the current input to the light emitting means so as to maintain the bit error rate at a pre-selected value.
  • such a data transceiver is operable to maintain a desired output power over a wide range of operating conditions.
  • an optical data transceiver comprising: a light emitting means operable to emit light in response to received electrical current; a processing means for controlling electrical signals input to said light emitting means; and a temperature sensing means operable to determine the temperature of the data transceiver and pass a signal indicative thereof to the processing means wherein the processing means is operable to maintain a desired output power level from the light emitting means by varying the current input to the light emitting means in accordance with a parabolic function of temperature.
  • a data transceiver is operable to maintain a desired output power over a
  • an optical data transceiver comprising: a light emitting means operable to emit light in response to received electrical current; a processing means for controlling electrical signals input to said light emitting means; a means for determining the bit error rate of light signals emitted by the light emitting means and passing a signal indicative thereof to the processing means and a temperature sensing means operable to determine the temperature of the data transceiver and pass a signal indicative thereof to the processing means wherein the processing means is operable to maintain a desired output power level from the light emitting means so as to maintain by varying the current input to the light emitting means in accordance with a parabolic function of temperature and further varying the current input in order to maintain the bit error rate at a pre-selected value.
  • a method of maintaining the power output of a light emitting means in a data transceiver at a desired level comprising the steps of: monitoring the bit error rate of data transmitted by the light emitting means; and varying the current input to the said light emitting means so as to maintain the bit error rate at a pre-selected value.
  • the method of the fourth aspect of the present invention may be implemented in an optical data transceiver according to the first aspect of the present invention.
  • a method of maintaining the power output of a light emitting means in a data transceiver at a desired level comprising the steps of: monitoring the temperature of the light emitting means; and varying the current input to the light emitting means in accordance with a parabolic function of temperature.
  • the method of the fifth aspect of the present invention may be implemented in an optical data transceiver according to the second aspect of the present invention.
  • a method of maintaining the power output of a light emitting means in a data transceiver at a desired level comprising the steps of: monitoring the bit error rate of data transmitted by the light emitting means; monitoring the temperature of the light emitting means; and varying the current input to the light emitting means in accordance with a parabolic function of temperature and further varying the input current so as to maintain the bit error rate at a pre-selected value.
  • the method of the sixth aspect of the present invention may be implemented in an optical data transceiver according to the third aspect of the present invention.
  • the light emitting means may be a laser and is preferably a VCSEL.
  • the optical data transceiver may be an optical transceiver of the type comprising a light emitting means and a light sensing means
  • the optical data transceiver may be an optical transceiver of the type comprising a light emitting means and not comprising a light sensing means.
  • the optical transceiver is packaged in a protective housing.
  • the protective housing is preferably provided with an aperture through which light can pass between the light emitting means and the exterior of the package.
  • the optical data transceiver is optically coupled to an optical fibre.
  • the aperture may be adapted to retain the optical fibre and align the optical fibre with the light emitting means.
  • the aperture may be formed to provide a reflector means for directing light between the light emitting means and the optical fibre.
  • a mounting means may be provided within the aperture to provide the retention and reflection functions.
  • the optical fibre may be a plastic optic fibre (POF) or a polymer cladded silica fibre (PCS).
  • the optical fibre may be terminated by a ferrule, if so, the aperture or mounting means may be adapted to receive and retain the ferrule.
  • said optical transceiver comprises an integrated circuit incorporating said light emitting means, said processing means and said temperature sensing means.
  • the light emitting means, processing means and temperature sensing means may be implemented on a single integrated circuit or may each be implemented on independent integrated circuits, said independent integrated circuits being electrically connected and physically fixed in a desired relative position.
  • the packaged optical data transceiver is mounted on a substrate.
  • said substrate is an application substrate such as a printed circuit board (PCB) or similar and said packaged optical data transceiver is electrically connected to said substrate.
  • PCB printed circuit board
  • the processing means includes non volatile memory means.
  • said non volatile memory means stores calibration data for use by said processing means in controlling the output of said light emitting means.
  • said calibration data is stored as part of a test and calibration process during manufacturing to accommodate both inherent and manufacturing tolerances.
  • the non volatile memory may also contain a pre-set value for the desired bit error rate.
  • the non volatile memory may also contain one or more constants to optimise said parabolic function for the specific characteristics of said light emitting means.
  • the pre-set bit error rate value may be used in calibration to determine the constants for optimising said parabolic function.
  • the bit error rate may be determined by monitoring signals received by another optical data transceiver.
  • the input current comprises a bias current and a modulation current.
  • the bias current may be varied in accordance with the parabolic function of temperature.
  • the modulation current may be varied in accordance with a linear function of temperature.
  • the modulation current may be constant below a predetermined threshold temperature and may be varied in accordance with a linear function of temperature above a predetermined threshold temperature.
  • an optical network comprising a plurality of optical data transceivers optically coupled to and interconnected by optical fibres, the power of transmission between individual optical data transceivers in the network being controlled according to the method of the fourth, fifth and sixth aspects of the present invention.
  • the network of the seventh or the eighth aspects of the present invention may incorporate any or all aspects of the first to sixth aspect of the present invention as are desired or appropriate.
  • the network of the seventh or the eighth aspects of the present invention may be used in vehicular or automotive control or entertainment systems such as those operating to the MOST standard.
  • Another application for such a network is in transmitting data between a digital imaging device and an image processing means for instance, those used in various automotive applications including lane following and parking assist.
  • Figure 1 is a schematic block diagram of an optical data transceiver according to a first aspect of the present invention
  • Figure 2 is a schematic block diagram of an optical data transceiver according to a second aspect of the present invention.
  • Figure 3 is a schematic block diagram of an optical data transceiver according to a third aspect of the present invention.
  • Figure 4 shows the variation in input modulation current and bias current with temperature in the second and third aspects of the present invention
  • Figure 5 is a schematic block diagram of circuitry for varying the bias current in accordance with figure 4.
  • Figure 6 is a schematic block diagram of circuitry for varying the modulation current in accordance with figure 4.
  • an optical data transceiver 100 comprises a light emitting means 101, a processing means 102 and a means for determining the bit error rate of light signals emitted by the light emitting means 103.
  • the light emitting means 101 is operable to emit light signals in response to input electrical current and may typically be a VCSEL.
  • the means for determining the bit error rate 103 is operable to output a signal indicative of the bit error rate to the processing means 102.
  • the processing means 102 is operable to control the current input to the light emitting means 101.
  • the processing means 102 raises the magnitude of the input current. As a result the output of the light emitting means 103 is increased in power until the measured bit error rate returns to the preset value.
  • the processing means 102 raises the magnitude of the input current. As a result the output of the light emitting means 103 is increased in power until the measured bit error rate returns to the preset value.
  • the processing means 102 raises the magnitude of the input current. As a result the output of the light emitting means 103 is increased in power until the measured bit error rate returns to the preset value.
  • the processing means 102 raises the magnitude of the input current.
  • the output of the light emitting means 103 is increased in power until the measured bit error rate returns to the preset value.
  • the output of the light emitting means 103 is decreased in power until the measured bit error rate returns to the preset value.
  • the processing means 102 may be provided with a non volatile memory for storing the preset bit error rate value or range.
  • the processing means may be operable to increase either or both of the bias current and the modulation current in the light emitting means.
  • FIG 2 a second embodiment of an optical data transceiver 100 is shown.
  • the means for determining the bit error rate is replaced by a temperature sensing means 104 operable to output a signal indicative of the temperature of the transceiver 100 to the processing means 102.
  • the processing means 102 is operable to vary the current input to the light emitting means 101 in response to variations in temperature. By varying the input current in this manner, it is possible to correct for variations in the power output of the light emitting means 101 caused by temperature variations.
  • the current variation may be made in accordance with a parabolic function of temperature. This is because it is desirable, as explained above, for the bias current to be similar to or greater than the threshold current for the light emitting means 101 and the threshold current typically varies according to a parabolic function of temperature.
  • the bias current might typically be varied according to a function of temperature of the following form (aa, bb and cc comprising particular bias current coefficients):
  • I ms (T,aa,bb,cc) aa - (ibb ' Ip TM J ⁇ r>*> 2 + cc -I CNST
  • I PTAT a-T + ⁇ is a current proportional to absolute temperature
  • I CNST is a constant current. This function is illustrated in figure 4 and can be
  • a bandgap current generator 201 generates constant
  • a process calibration unit 202 typically a 5 bit IDAC.
  • a 5 bit process is used
  • I PTAT is output from
  • multiplier unit 205 and fed to squarer unit 206.
  • the output of squarer unit 206 is
  • IDAC 207 typically a 6 bit IDAC.
  • I CNST is also fed
  • IDAC 208 typically a 5 bit IDAC
  • cc coefficient of the cc
  • the 10 outputs of IDACs 207 and 208 are fed to adder unit 209 which adds them together to output the required bias current.
  • the modulation current may also be varied in addition to the bias current.
  • the modulation current would be varied according to a simpler function of temperature.
  • One suitable such example is:
  • bias current generator I CNST and I PTAT are generated by a bandgap current generator
  • a process calibration unit 302 typically a 5 bit IDAC.
  • Units 303 and 304 generate the linearly varying current if T>TC (whilst the current is referred to herein as linearly varying, it may of course be
  • I CNST is
  • the extinction ratio (modulation depth) can be increased to a minimum of 22 over the complete temperature range.
  • both a temperature sensor 104 and a means for determining the bit error rate 103 are provided.
  • the processing means uses information from both the temperature sensing means 104 and the bit error rate means 103 in calculating how to vary the current input to the light emitting means 101 in order to maintain the output power at a desired level.
  • the bit error rate means 103 is used to calibrate the parameters of the parabolic function of temperature.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)

Abstract

L’émetteur/récepteur optique 100 comprend un moyen d’émission de lumière 101, un moyen de traitement 102 et un moyen de détermination du taux d’erreurs binaires de signaux de lumière émis par le moyen d’émission de lumière 103. Lorsque le taux d’erreurs binaires dépasse une valeur préréglée, le moyen de traitement 102 augmente l’amplitude du courant d’entrée. En conséquence, la sortie du moyen d’émission de lumière 103 augmente en puissance jusqu’à ce que le taux d’erreurs binaires revienne à la valeur préréglée. Lorsque le taux d’erreurs binaires descend en dessous d’une valeur préréglée, le moyen de traitement 102 diminue l’amplitude du courant d’entrée. En conséquence, la sortie du moyen d’émission de lumière 103 diminue en puissance jusqu’à ce que le taux d’erreurs binaires revienne à la valeur préréglée. Selon un autre exemple de mode de réalisation, le moyen de détermination du taux d’erreurs binaires est remplacé par un moyen détectant la température 104 pouvant fournir un signal indiquant la température de l’émetteur/récepteur optique 100 au moyen de traitement 102 et le moyen de traitement 102 peut faire varier l’entrée de courant du moyen d’émission de lumière 101 en réaction aux variations de température. La variation de courant peut correspondre à une fonction parabolique de la température. En faisant varier de cette manière le courant d’entrée, il est possible de corriger les variations de sortie de puissance du moyen d’émission de lumière 101 causées par des variations de température.
PCT/IB2006/003593 2005-12-15 2006-12-13 Émetteur/récepteur de données optique économique Ceased WO2007069045A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0525521.1 2005-12-15
GB0525521A GB0525521D0 (en) 2005-12-15 2005-12-15 Low cost optical data tranceiver

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WO2007069045A1 true WO2007069045A1 (fr) 2007-06-21

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130219697A1 (en) * 2012-02-23 2013-08-29 Sumitomo Electric Device Innovations, Inc. Method to produce optical transceiver
CN113055092A (zh) * 2021-03-17 2021-06-29 卡斯柯信号有限公司 一种提高既有信号设备通信传输安全性的设备和方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0744800A2 (fr) * 1995-05-22 1996-11-27 Nec Corporation Circuit de commande d'une diode laser
WO1998000893A1 (fr) * 1996-07-01 1998-01-08 Pacific Fiberoptics, Inc. Emetteurs intelligents a fibre optique et procedes d'exploitation et de fabrication correspondants
WO1999053577A1 (fr) * 1998-04-14 1999-10-21 Optobahn Corporation Correcteur de temperature de diodes laser
WO2001050556A1 (fr) * 1999-12-30 2001-07-12 Sycamore Networks, Inc. Polarisation et essai sur circuit d'un laser dans une carte d'emetteur-recepteur wdm
WO2003058827A2 (fr) * 2001-12-27 2003-07-17 Ceyx Technologies, Inc. Systeme de regulation integree d'une optique de laser et procede de fonctionnement dudit systeme

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0744800A2 (fr) * 1995-05-22 1996-11-27 Nec Corporation Circuit de commande d'une diode laser
WO1998000893A1 (fr) * 1996-07-01 1998-01-08 Pacific Fiberoptics, Inc. Emetteurs intelligents a fibre optique et procedes d'exploitation et de fabrication correspondants
WO1999053577A1 (fr) * 1998-04-14 1999-10-21 Optobahn Corporation Correcteur de temperature de diodes laser
WO2001050556A1 (fr) * 1999-12-30 2001-07-12 Sycamore Networks, Inc. Polarisation et essai sur circuit d'un laser dans une carte d'emetteur-recepteur wdm
WO2003058827A2 (fr) * 2001-12-27 2003-07-17 Ceyx Technologies, Inc. Systeme de regulation integree d'une optique de laser et procede de fonctionnement dudit systeme

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20130219697A1 (en) * 2012-02-23 2013-08-29 Sumitomo Electric Device Innovations, Inc. Method to produce optical transceiver
US9089084B2 (en) * 2012-02-23 2015-07-21 Sumitomo Electric Device Innovations, Inc. Method to produce optical transceiver
CN113055092A (zh) * 2021-03-17 2021-06-29 卡斯柯信号有限公司 一种提高既有信号设备通信传输安全性的设备和方法
CN113055092B (zh) * 2021-03-17 2022-07-12 卡斯柯信号有限公司 一种提高既有信号设备通信传输安全性的设备和方法

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