The present invention relates to a method for tuning the wavelengths of optoelectronic components in an optoelectronic component array.
The present invention also relates to an optoelectronic component array having at least two optoelectronic components where each individual optoelectronic component of the component array has an associated resistance heater for setting the characteristic wavelength of the optoelectronic component.
Optical transmission systems are being increasingly used for the transmission of data and for the transmission of television and radio channels. Generally, such optical transmission systems include a light-conducting waveguide, and a solid-state laser as a light generator and a light detector. The solid-state laser emits light of a defined, characteristic wavelength. This characteristic wavelength is essentially dependent on the material used, but it can be set within a defined wavelength range, for example, by the action of heat. To increase the volume of data that can be transmitted through a waveguide, it is possible to employ a plurality of solid-state lasers associated with a waveguide, the solid-state lasers operating with different wavelengths. In this connection, however, precise adherence to the wavelengths is needed, making it possible for the data to be differentiated unambiguously at the end of the transmission.
Since, for reasons inherent to the manufacturing process, the characteristic wavelengths of solid-state lasers vary within a tolerance range, it is necessary for the solid-state lasers to be tuned before they are used for the transmission of data. So-called resistance heaters, for example, are used for this purpose, the resistance heaters changing the characteristic wavelength of a solid-state laser through the action of heat. Generally, tuning is accomplished by adjusting the voltage applied to the resistance heater, a separate voltage source being associated with each resistance heater and, thus, with each optoelectronic component of the component arrangement.
However, this entails the disadvantage that a very complex design is required. Furthermore, later tuning of the arrangement is not easily possible.
An object of the present invention, therefore, is to provide a method and device for tuning optoelectronic components, the method and device being simple and able to be implemented at low cost.
The method and device according to the present invention the principle of thermally changing the resistance heaters of the optoelectronic components of the optoelectronic component array in question.
In the method according to the present invention wavelength is measured for each optoelectronic component of the optoelectronic component array. On the basis of a comparison of the measured wavelength with the desired characteristic wavelength, the deviation from the desired characteristic wavelength is determined for each optoelectronic component of the optoelectronic component array. Next, according to the present invention, a resistor arrangement associated with the respective optoelectronic component is modified as a function of the ascertained wavelength deviation. By way of its total resistance, the resistor arrangement, which is connected upstream of the heater of the optoelectronic component, influences the heating power of the heater of the optoelectronic component. The total resistance of the resistor arrangement is set such that, by way of the heating power, the desired characteristic wavelength of the optoelectronic component in question is obtained. This procedure is carried out on an individual basis for each optoelectronic component of the optoelectronic component array. The method according to the present invention permits the very simple setting of the optoelectronic components of a component array, such as a row of solid-state lasers. In particular, the method can be performed fully automatically, which is a significant advantage when optoelectronic components are used on a large scale.
The present invention provides for its component array to include resistor arrangements RM, in addition to a common voltage source U0. Each optoelectronic component of the component array is associated with a separate resistor arrangement RM. The resistor arrangement RM is disposed between common voltage source U0 and resistance heater H; i.e., a separate resistor arrangement RM is connected upstream from each resistance heater H. Each resistor arrangement RM is composed of a network of resistors R. Consequently, the heating power for each optoelectronic component of the optoelectronic component array can be set easily by making corresponding changes to the resistor network. Since all resistor arrangements RM are supplied by a single voltage source U0, the need is eliminated for a substantial amount of circuitry, resulting in cost savings. A further advantage is that the characteristic wavelengths of the optoelectronic components can also be subsequently tuned in a simple manner by changing the total resistance and, thus, the heating power.
An embodiment of the present invention provides for configuring resistor arrangement RM in the form of a resistor array, which includes a plurality of resistor elements arranged systematically according to resistance values. Preferably, resistor arrangement RM includes one or more rows of contact fields K, the resistors of resistor arrangement RM being disposed between individual contact fields K. The total resistance of resistor arrangement RM and, thus, the heating power of the heater of the optoelectronic component can be altered by switching or bypassing contact fields K. Since contact fields K and the resistors are arranged according to logical aspects, the heating power can be simply set by the manner in which contact fields K are interconnected, it being possible to determine the specifically required connections from the systematic nature of the matrix. At the same time, the method according to the present invention also makes it possible to adapt the heating power, at any time, as needed.
The present invention is explained in greater detail below with reference to the drawings, in which:
a shows a schematic representation of a resistor apparatus;
b shows a circuit diagram of the resistor apparatus;
c shows graphs depicting how the heating powers of different channels influence each other;
a shows a schematic diagram of embodiment of a component array;
b to 4d show three graphs for determining the heating power;
a shows a schematic diagram of another embodiment of a component array;
b shows a graph for calculating the heating power;
a shows a schematic diagram of an embodiment of a component having the resistor array on the row of components;
b shows a schematic illustrating a method for wavelength tuning in an optoelectronic component array;
a shows a schematic diagram of an embodiment of a component array including a current source; and
b shows a circuit diagram representing the component array of
For this purpose, each solid-state laser Ll to Ln is associated with at least one resistance heater Hl to Hn. Each of resistance heaters Hl to Hn is made up of a current conductor, which has a suitably high resistance and generates heat when a voltage is applied, and produces a temperature field in the respective solid-state laser Ll–Ln. To produce the desired temperature field, it is necessary in many cases for the heating power to first be adjusted. To this end, each resistance heater Hl–Hn is connected, according to the present invention, to a separate resistor array RMl–RMn. All resistor arrangements RMl–RMn are connected to a common voltage source U0 and are supplied by it. Resistor arrangements RMl–RMn may be in the form of resistor arrays composed of individual resistors. By selectively manipulating the individual resistors, one selectively changes the total resistance of the resistor arrangement, configured as a resistor array. Changing the total resistance of the individual resistor arrangements RMl–RMn effects a change in the current flowing through resistance heaters Hl–Hn and, therefore, in the heating power of individual resistance heaters Hl–Hn. The wavelength is altered on an individual basis by varying the heating power of individual resistance heaters Hl–Hn until the desired characteristic wavelength is set for each individual solid-state laser Ll–Ln. The resistors of resistor arrangements RMl–RMn are set to defined resistance values electrically, optically and/or by electromagnetic waves. Resistor arrangements RMl–RMn can, on the one hand, be disposed on a substrate/insulator carrying solid-state lasers Ll–Ln. Resistor arrangements RMl–RMn can also be disposed separately from solid-state lasers Ll–Ln, for example at a later, easily accessible location of the entire data transmission unit.
As already mentioned, characteristic wavelength λq of each individual optoelectronic component, such as of solid-state lasers Ll–Ln, can be individually set by varying the temperature of each individual solid-state laser Ll–Ln and, therefore, by way of heating power Pq, or heating current Iq, through resistance heaters Hl–Hn. The basis for individually setting the heating current for each channel q, with q ε [l−n] is provided by the matrix-like arrangement of resistor arrangements RMl–RMn.
The arrangement, including voltage source U0, electrical connections LQ, the matrix-like arrangement of contact fields, ohmic resistors Rq,ij→q,k,l between contact fields Kq,i, j and Kq,k,l, is manipulated or tuned according to the present invention in such a way that a heating power Pq automatically adjusts itself at electrical resistance heater Hq, giving rise to a temperature change ΔTq at solid-state laser Lq due to the thermal coupling of resistance heater Hq to solid-state laser Lq. This temperature change causes a wavelength shift Δλq of the characteristic wavelength of channel q. Wavelength λq of channel q is individually set in accordance with the following method:
At the beginning of the process, a heating power Pq≧0 is set, the heating power resulting in a wavelength λq. The aim is to set the heating power, such that the wavelength is λq,s.
The resistance heater's heating power is varied within a range in which the associated change in wavelength covers the range of desired wavelength λq,s. This measurement yields a functional relationship λq(Pq). Accordingly, it is possible, from the relationship, to determine heating power Pq for a wavelength λq,s. The desired heating power Pq can be set by changing resistor arrangement RMq. Heating power Pq can also be varied by adjusting the voltage at voltage source U0, it being the case, however, that the heating powers of the other optoelectronic components are also altered accordingly. The maximum amount of the power variation ΔPqPq=Pq,max–Pq,min of a channel q is defined by the magnitude of the voltage applied to contact fields Kq,v,w and Kq,v,w, the dimensioning and arrangement of resistors Rq,ij→q,k,l, and by short circuits between the contact fields, as well as by dimensionally sizing heating resistor Pq of resistance heater Hq. This power variation ΔPq results in a maximum wavelength variation Δλq,max.
A further possibility for setting the characteristic wavelength provides for setting heating power Pq to a defined value P≧0 and for measuring the associated wavelength. Heating power Pq is then changed on the basis of stored empirical values for the functional relationship λq(Pq).
It is also conceivable to successively set heating power Pq to two values and, each time, to measure the associated wavelength. The characteristic of functional relationship λq(Pq) is subsequently calculated by interpolation and/or extrapolation of the previously determined wavelengths, and heating power Pq is changed accordingly.
It is equally conceivable to vary heating power Pq at intervals, in defined steps ΔP, and to measure the corresponding wavelength to produce functional relationship λq(Pq), and to vary heating power Pq on the basis of the determined relationship.
It is, of course, also possible to continuously vary heating power Pq until the desired characteristic wavelength is obtained.
When adjusting heating power Pq, the following requirement is met for the resistance values of connections LQ between voltage source U0 and the matrix-like arrangement of contact fields Kq,i,j–Kq,k,l, as well as the internal resistance of voltage source U0: if, given a component arrangement of n channels having n resistance heaters and n arrangements of contact fields, a number of n-1 resistance heaters H has a heating power Pe,min, and any resistance heater Hs has heating power Ps, where Ps,min<Ps<Ps,max and s≠e, then electrical connections LQ of voltage source U0 having the contact fields of individual channels q, as well as the internal resistance of voltage source U0 are dimensionally designed such that, in response to a variation in the heating powers of n-1 channels by ΔPe,i.e., from Pe,min to Pe,max, the heating power of resistance heater Hs varies by a value ΔPs,error<εs•ΔPs, with a value 0<εs<1 which is freely selectable, but which should be as small as possible, to minimize the cross-influencing of the channels.
b shows the circuit diagram of an embodiment of the present invention including three resistance heaters. In this simple case, the matrix-like arrangement of contact fields is such that they can be combined to form total resistances (referred to in the following as series resistors PV1–RV3) which can be connected in series with heating resistor RH1–RH3. Electrical connections LQ of voltage source U0 to the contact fields leading to total resistors RV1–RV3 and heating resistors RH1–RH3 feature a line resistance RL1–RL3. The internal resistance of voltage source U0 is contained in resistor RL1.
The resistance values of series resistors RV1–RV3 and heating resistors RH1–RH3 are dimensioned according to required heating powers P1–P3 or wavelength shifts and the magnitude of available voltage U0. Line resistances RL1–RL3 must meet the above requirement. The powers of heating resistors RH1–RH3 result from: Pq=I2qRHq where q=1,2,3 and RHq, =resistance of the q-th heater Hq
and from the currents
and
c shows the aforementioned requirement for channel 1. Heating power P1 of channel 1 has any value within ΔP1. The remaining channels 2 and 3, respectively, have heating powers of P2,min and P3min. If the heating powers of channels 2 and 3 are raised to P2,max and P3,max, the deviation from P1, must be less than ε1•ΔP1.
The following briefly shows the calculation of the resistances RL1 to RL3:
where
From the above three equations, it is possible to calculate the maximum values of line resistances RL1, RL2, RL3.
Furthermore, the first part of the arrangement includes resistance heaters H1 to H6, as well as a part of the contact fields of contact matrix (K1–K4; K13–K16; K25–K28), H1, H2 and K1–K4 belonging to channel 1, H3, H4 and K13–K16 being associated with channel 2, and H5, H6 as well as K25–K28 being assigned to channel 3. The resistance heaters H1–H6 are arranged such that they are in thermal contact with solid-state lasers L1 to L3 associated with them.
The second part of the arrangement includes an insulator on which is situated—for each channel, i.e., for each solid-state laser L1 to L3—the second part of the contact fields of contact matrix (K5 to K12 for channel 1, K17 through K24 for channel 2, and K29 through K36 for channel 3). In the present case, the contact matrix is a one-dimensional matrix having twelve fields. Leads LQ to voltage source U0 are at the upper edge of the row of lasers and at the lower edge of the row of contacts. The leads include the following regions: A0, B, A1, K25, B, K26, A2, K13, B, K14, A3, K1, B, K2 as well as, on the insulators, A4, K36, A5, K24, A6, K12, B being bond connections.
Consequently, the leads contain regions of the contact matrices.
Situated next to the contact matrices on the contact arrangement are further contact fields KL1 to KL3, which are connected by electrically conducting bond connections B to the contacts of the rows of lasers L1–L3. Contact fields K5 to K12 of channel 1, K17 through K24 of channel 2, and K29 through K36 of channel 3 of the contact matrices are provided with an electrically conducting connection to resistors R1–R7; R8–R14 and R15–R21 by spatially distributed resistor arrangements. In
The resistance heaters H1–H6 are set to a defined heating power Pq by changing the resistances between the contacts of the contact matrix, it also being possible to implement this by adding electrical connections or by changing the loop-shaped resistor arrangements.
The extent to which the heating power required during the tuning process varies is adjusted by a variable voltage at voltage source U0.
The embodiment of the present shown in
Binary coding of the resistance values may be used, making it possible to span a resistance range from R to R/2i, i being the number of resistors per channel. Thus, given five resistors, thirty-one different resistance values can be set. For example, for channel 1, electrically conducting connections are established from contact field K5 to contact fields K6 to K10. If, for example, resistance value ⅙·R is to be set for channel 1, then, as implemented in
For the case that U0=2.5 V,R=480 ohm and RH=20 ohm,
Rres being the resultant resistance.
The relative increment, or step size, is plotted on the right-hand ordinate axis in
It may be advantageous, for high heating powers, for example, to adjust heating power Pq in disproportionately small (large) increments, as is done in
a shows a variation of
For example, there is a resultant resistance of R1+R3+R4+R6 for solid-state laser L1. The same applies to the remaining channels.
b shows the variation in power for the case of binary coding. With reference to channel 2, it is shown how it is possible to achieve further total resistance values with any combination of overlapping connections between the contact fields, for example through connections between contact fields K17 and K19, as well as K18 and K20.
The contact matrix shown in
The embodiment of the present shown in
The embodiment of the present shown in
In the embodiment of the present invention shown in
a depicts an embodiment of the present in which the resistors of resistor arrangement RM are disposed on the row of components, with the result that resistor arrangement RM is tuned on the row of components.
At this point, the above-described method for tuning solid-state lasers Ll to Ln shall be briefly explained once again with reference to
It becomes clear from the aforementioned embodiment of the present that there is a multiplicity of possibilities for individually setting the heating powers Pq of individual resistance heaters Hl–Hn in simple manner using resistor arrangement RMl–RMn according to the present invention, without having to revert to a plurality of voltage sources U0. In particular, individual resistors Rl–Rn or RI–RV, etc., of resistor arrangements RMl–RMn can be changed at any time, even afterwards, following initial operation of the component array. Thus, it is conceivable, for example, to change the wavelength or heating power Pq using time and temperature measurements on the basis of empirical values, in order, for example, to compensate for aging effects.
In addition, the present invention can be applied not only to the described solid-state lasers Ll–Ln, but in general to optoelectronic components, such as optical amplifiers, filters, wavelength multiplexers or waveguides.
In the aforementioned embodiments of the present, a voltage source U0 is used in each case as the energy supply apparatus. Of course, it is also possible to use a current source I, as shown in
Number | Date | Country | Kind |
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197 55 457 | Dec 1997 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP98/06911 | 10/21/1998 | WO | 00 | 8/25/2000 |
Publishing Document | Publishing Date | Country | Kind |
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WO99/28998 | 6/10/1999 | WO | A |
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