WO2004044637A1

WO2004044637A1 - To-can package for 10gbps optical module

Info

Publication number: WO2004044637A1
Application number: PCT/KR2003/002459
Authority: WO
Inventors: Ji Chai Jeong; In-Ho Choi; Heon Wi Ryu; Myoung Ki Yoo
Original assignee: RAPIDUS Inc
Current assignee: RAPIDUS Inc
Priority date: 2002-11-14
Filing date: 2003-11-14
Publication date: 2004-05-27
Anticipated expiration: 2005-05-14
Also published as: AU2003284721A1; KR100456308B1; JP2006506807A; KR20040042922A

Abstract

The present invention discloses a TO-CAN package for a 10Gbps optical module including a stem for receiving an optical device, and a lead connected to the optical device through an opening of the stem. The package includes an RF feed line having a first lead being covered with a first insulation layer by a predetermined length from the outside to the ingress of the opening of the stem, and existing outside the TO-CAN package, a second lead passing through and existing in the opening of the stem filled with a second insulation layer, and a third lead existing in the TO-CAN package, at least part of the circumference of which being covered with a third insulation layer by a predetermined length, the first to third leads being incorporated in a single body.

Description

TO-CAN PACKAGE FOR 10GBPS OPTICAL MODULE

TECHNICAL FIELD

The present invention relates to a TO-CAN package for a 10Gbps optical module, and more particularly to, a TO-CAN package for a 10Gbps optical module which can improve impedance matching p roperties by covering a lead passing through an opening of a stem with a plurality of insulation materials according to their positions.

BACKGROUND ART

Recently, an optical communication system requires large capacity data transmission as well as long distance transmission. Same market trends are found in a local area network (LAN) or metropolitan area network (MAN) such as a Gigabit Ethernet used as an access network. Major devices for such applications need both a large bandwidth for high rate data transmission and price competitiveness. As light sources for satisfying such demands, TO-CAN package type laser diodes (LD) and photodiodes (PD) gain popularity because of their low prices.

In general, a chip state size of an optical device such as the LD and PD ranges from 300μmχ300μm to 500μmχ500μm, and a basic substance of the optical device is lll-V group compound semiconductor. It is thus difficult to handle the optical device due to low fracture toughness. In addition, when the optical device is exposed to external moisture or temperature, the optical device may be deteriorated or performance thereof may be reduced. Accordingly, in order to protect the optical device and maintain its performance, the optical device is generally mounted and modularized in a TO-CAN package. In the case of the LD TO-CAN package, a data signal inputted from an external system is transmitted to the inside of the TO-CAN package through a lead inserted into the TO-CAN package, and then transmitted to the LD or PD through a wire-bonded wire. Here, the transmitted electric data signal is converted into an optical data signal by the LD, and the optical data signal is discharged to be incident on an optical transmission medium such as an optical fiber. For high data rate transmission, the electric data s ignal transmitted through the l ead needs a transmission medium having a large bandwidth over a few GHz.

A conventional TO-CAN package structure includes a stem for receiving an optical device and a lead for transmitting a data signal. Various stem structures having the outer diameter of 3.8mm, 5.4mm or 5.6mm can be used. An RF feed line is inserted through a small hole which allows the lead to be inserted into or passed through the stem structure, and has a coaxial structure using glass as an insulation material and showing an impedance of 17Ω to 24Ω. The conventional TO-CAN package structure is very simple and transmits

2.5Gbps data, but is not able to transmit 10Gpbs high rate data.

Fig. 1 is a perspective view illustrating a conventional TO-CAN package. The TO-CAN package 1 has a symmetrical structure and Fig. 1 shows a half of the whole structure. The TO-CAN package 1 includes a stem 10 for receiving an optical device (not shown), an opening 30 formed on the stem 10, a lead 20 passing through the opening 30, and a glass layer 40 filled in the opening 30 for covering the lead 20. That is, at least, the TO-CAN package 1 includes an RF feed line 2 (explained later in Fig. 2d) comprised merely of the lead 20, the stem 10, and the opening 30 of the stem 10 for covering the lead 20 with the glass layer 40. The conventional TO-CAN package of Fig. 1 matches an impedance between 17Ω and 24Ω, by sealing up glass which is an insulation material between the lead inserted R2003/002459

through the opening of the stem and the stem body.

Fig. 2A is a plan view illustrating the TO-CAN package of Fig. 1.

Fig. 2B is a left side view illustrating the TO-CAN package of Fig. 1.

Fig. 2C is a right side view illustrating the TO-CAN package of Fig. 1. Fig. 2D is a cross-sectional view illustrating the TO-CAN package of Fig. 1 , taken along line A-A'. As illustrated in Fig. 2D, the conventional TO-CAN package 1 has a coaxial structure for covering the lead 20 with the glass layer 40 in the opening 30 of the stem 10. That is, the TO-CAN package 1 includes the RF feed line 2 having the lead 20 which signals are inputted to, the lead 20 inserted into the stem 10, and the lead 20 existing in the TO-CAN package 1 (except the glass layer 40 in the opening 30).

According to test conditions of performance of the TO-CAN package, a measured object frequency band ranges from 1GHz to 10GHz, and the length of the lead 20 is a=14mm, b=1.2mm and c=0.7mm (same in the whole embodiments). Table 1 shows the other conditions.

Fig. 3A is a graph showing reflection loss (I S11| ) of the TO-CAN package of Fig. 1. In detail, when the data is intended to be transmitted at a high rate by using the TO-CAN package 1 of Fig. 1 , the reflection loss (l S11| ) of the input data signal is linearly reduced because of impedance mismatching between the lead 20 exposed to the air and the lead 20 inserted into the stem 10, and impedance mismatching between the lead 20 inserted into the stem 10 and the lead 20 existing in the TO-CAN package 1.

That is, the reflection loss (I S11| ) is maintained approximately to 14dB in low frequencies, but linearly reduced in high frequencies, for example about 6dB in

10GHz.

Fig. 3B is a graph showing transmittance (I S21| ) of the TO-CAN package of Fig. 1. Referring to Fig. 3B, the transmittance (I S21| ) has values of -1.7dB to

-0.1 dB in the range of 1 GHz to 10GHz. Accordingly, when the reflection loss (I S11| ) is small, it is difficult to use the

TO-CAN package in the module for transmitting 10Gbps of high rate data.

In order to use the TO-CAN package for 10Gbps, the reflection loss (I S11| ) to 10GHz must be larger than 10dB. However, the conventional TO-CAN package cannot satisfy such specification or standard. In the conventional TO-CAN package structure, the reflection loss (I S11| ) of the input data signal is reduced smaller than 10dB in 10GHz because of impedance mismatching between the lead 20 exposed to the air for receiving the data signal and the lead 20 inserted into the stem 10, and impedance mismatching between t he lead 20 inserted into the s tern 1 0 a nd t he lead 20 e xisting i n t he TO-CAN package 1. That is, the lead 20 inserted into the stem 10 has an impedance of about 20Ω, but the lead 20 exposed to air and the lead 20 existing in the TO-CAN package 1 have an i mpedance of a few tens Ω, which g enerates impedance mismatching.

In addition, the conventional TO-CAN package structure is not suitable for 10Gbps of high data rate transmission because a parasitic capacitance between the leads 20 in the stem 10 is very high, about 0.459pF. DISCLOSURE OF THE INVENTION

An object of the present invention is to improve reflection loss and transmittance properties which cause problems to a general TO-CAN package. Another object of the present invention is to provide a new RF feed line structure which can achieve application of a TO-CAN package to a lOGbps high rate data t ransmission module, b y maintaining a low parasitic c apacitance in a stem by increasing a distance between a lead inserted into the stem and the stem. In order to achieve the above-described objects of the invention, there is provided a TO-CAN package for a lOGbps optical module including a stem for receiving an optical device, and a lead connected to the optical device through an opening of the stem, the package including an RF feed line having a first lead being covered with a first insulation layer by a predetermined length from the outside to the ingress of the opening of the stem, and existing outside the TO-CAN package, a second lead passing through and existing in the opening of the stem filled with a second insulation layer, and a third lead existing in the TO-CAN package, at least part of the circumference of which being covered with a third insulation layer by a predetermined length, the first to third leads being incorporated in a single body. Preferably, the second lead is covered with the second insulation layer. Preferably, the first lead further includes a first grounding conductor for covering the first insulation layer by the predetermined length.

Preferably, the third lead further includes a second grounding conductor for covering the third insulation layer by the predetermined length.

Preferably, the second grounding conductor covers half of the circumference of the third lead with the third insulation layer between the second grounding conductor and the third lead. Preferably, the first insulation layer is a glass layer, the second insulation layer is an air layer, the third insulation layer is an air layer, and the second grounding conductor covers part of the circumference of the third lead with a predetermined interval from the third lead. Preferably, the first insulation layer is a glass layer, the second insulation layer is a glass layer, the third insulation layer is an air layer, and the second grounding conductor covers part of the circumference of the third lead with a predetermined interval from the third lead.

Preferably, the first insulation layer is a glass layer, the second insulation layer is a glass layer, and the third insulation layer is a glass layer.

Preferably, t he first i nsulation I ayer i s an air I ayer, the second i nsulation layer is a glass layer, the third insulation layer is an air layer, the first grounding conductor covers the circumference of the first lead by the predetermined length with a predetermined interval from the first lead, and the second grounding conductor covers part of the circumference of the third lead with a predetermined interval from the third lead.

Preferably, an impedance of the first lead of the RF feed line is matched to a predetermined value with an impedance of the second lead and an impedance of the third lead. According to one aspect of the invention, an RF feed line for a TO-CAN package including a stem for receiving an optical device, and a lead connected to the optical device through an opening of the stem, the RF feed line having a first lead covered with a first insulation layer by a predetermined length from the outside to the ingress of the opening of the stem, and p ositioned o utside t he T O-CAN package, a second lead positioned inside the opening of the stem, and a third lead positioned inside the TO-CAN package, at least part of the circumference of which being covered with a third insulation layer, the first to third leads being incorporated in a single body.

According to another aspect of the invention, a method for manufacturing an RF feed line for a TO-CAN package including a stem for receiving an optical device, and a lead connected to the optical device through an opening of the stem, the method including the steps of: covering a lead positioned outside the TO-CAN package with a first insulation layer by a predetermined length to the opening of the stem; and covering at least part of the circumference of a lead positioned inside the TO-CAN package with a second insulation layer. Preferably, the method further includes a step for covering the first insulation layer with a first grounding conductor by the predetermined length.

Preferably, the method further includes a step for covering the second insulation layer with a second grounding conductor by the predetermined length. Preferably, the second grounding conductor covers half of the circumference o f the lead w ith the s econd i nsulation I ayer b etween the s econd grounding conductor and the lead.

Preferably, the first insulation layer is a glass layer, the second insulation layer is an air layer, and the second grounding conductor covers part of the circumference of the lead with a predetermined interval from the lead. Preferably, the first insulation layer is a glass layer, the second insulation layer is an air layer, and the second grounding conductor covers part of the circumference of the lead with a predetermined interval from the lead.

Preferably, the first insulation layer is a glass layer, and the second insulation layer is a glass layer. Preferably, t he first i nsulation I ayer i s an air I ayer, the second i nsulation layer is an air layer, the first grounding conductor covers the circumference of the lead by the predetermined length with a predetermined interval from the lead, and the second grounding conductor covers part of the circumference of the lead with a predetermined interval from the lead.

Preferably, the method further includes a step for covering the lead positioned inside the opening of the stem with a third insulation layer.

Preferably, the third insulation layer is one of an air layer and a glass layer.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view illustrating a conventional TO-CAN package; Figs. 2A to 2D are a plan view, a left side view, a right side view and a cross-sectional view (A-A') illustrating the TO-CAN package of Fig. 1 , respectively; Figs. 3A and 3B are graphs showing reflection loss and transmittance of the TO-CAN package of Fig. 1 , respectively;

Fig. 4 is a perspective view illustrating a TO-CAN package in accordance with a first embodiment of the present invention;

Figs. 5A to 5D are a plan view, a left side view, a right side view and a cross-sectional view (A-A') illustrating the TO-CAN package of Fig.4, respectively;

Figs. 5E and 5F are a w hole I eft s ide v iew and a whole right side view illustrating the TO-CAN package in accordance with the present invention; Figs. 6A and 6B are graphs showing reflection loss and transmittance of the

TO-CAN package of Fig. 4, respectively;

Fig. 7 is a perspective view illustrating a TO-CAN package in accordance with a second embodiment of the present invention;

Figs. 8A to 8D are a plan view, a left side view, a right side view and a cross-sectional view (A-A') illustrating the TO-CAN package of Fig. 7, respectively;

Figs. 9A and 9B are graphs showing reflection loss and transmittance of the TO-CAN package of Fig. 7, respectively;

Fig. 10 is a perspective view illustrating a TO-CAN package in accordance with a third embodiment of the present invention;

Figs. 11A to 11 D are a plan view, a left side view, a right side view and a cross-sectional view (A-A') illustrating the TO-CAN package of Fig. 10, respectively;

Figs. 12A and 12B are graphs showing reflection loss and transmittance of the TO-CAN package of Fig. 10, respectively;

Fig. 13 is a perspective view illustrating a TO-CAN package in accordance with a fourth embodiment of the present invention;

Figs. 14A to 14D are a plan view, a left side view, a right side view and a cross-sectional view (A-A') illustrating the TO-CAN package of Fig. 13, respectively; and

Figs. 15A to 15F are graphs showing reflection loss and transmittance when grounding conductors of the first to third embodiments differently cover leads.

BEST MODE FOR CARRYING OUT THE INVENTION

A TO-CAN package for a 10Gbps optical module in accordance with the present invention will now be described in detail with reference to the accompanying drawings.

In the following description, same drawing reference numerals are used for the same elements even in different drawings.

Fig. 4 is a perspective view illustrating a TO-CAN package in accordance with a first embodiment of the present invention. The TO-CAN package 100 has a symmetrical structure and Fig. 4 shows a half of the whole structure (same in the following). The TO-CAN package 100 includes a stem 10 for receiving an optical device (not shown), an opening 30 (not shown) formed in a predetermined position of the stem 10, a lead 20 passing through the opening 30, an air layer 41 (not shown) filled in the opening 30 for covering the lead 20, a grounding conductor 60 adhered to the surface of the stem 10 outside the TO-CAN package 100 and filled with a glass layer 31 , for covering the lead 20, and a grounding conductor 61 adhered overlapping with the surface of the stem 10 and the opening 30 inside the TO-CAN package 100, for covering part of the lead 20, an interval between the grounding conductor 61 and the lead 20 being filled with an air layer 51 (not shown).

Figs. 5A to 5D are a plan view, a left side view, a right side view and a cross-sectional view (A-A') illustrating the TO-CAN package of Fig.4, respectively.

As illustrated in Fig. 5A, the grounding conductor 61 covers part of the lead

20 with a predetermined interval from the lead 20, and the interval is filled with the air layer 51.

As shown in Fig. 5B, the grounding conductor 60 covers a glass layer 50 covering the lead 20, and the grounding conductor 61 covers part of the lead 20 existing in the TO-CAN package 100 with the air layer 51 between the grounding conductor 61 and the lead 20. The grounding conductor 61 is adhered to the stem 10, overlapping with the stem 10 and the opening 30.

Fig. 5C shows the grounding conductor 61 adhered overlapping with the opening 30 of the stem 10.

Referring to Fig. 5D, the lead 20 positioned outside the TO-CAN package

100 for receiving an electric signal has a coaxial structure covered with the grounding conductor 60 filled with the glass layer 50, and the lead 20 existing in the opening 30 of the stem 10 has a floating structure covered with the air layer 41. In addition, part (for example, half) of the whole circumference of the lead 20 existing in the TO-CAN package 100 is covered with the grounding conductor 61 with the air layer 51 between the grounding conductor 61 and the lead 20. The residual part of the lead 20 is exposed to air for bonding. That is, the TO-CAN package 100 includes an RF feed line 200 (indicated by a dotted line, except the air layer 41 in the opening 30) comprised of the lead 20 receiving a signal and being covered with the grounding conductor 60, the glass layer 50 being filled between the lead 20 and the grounding conductor 60, the lead 20 i nserted into the stem 10, and the lead 20 h aving its p art covered with the grounding conductor 61 in the TO-CAN package 100. The RF feed line 200 has an insulation structure of glass-air-glass. In addition, impedances are matched in the whole parts by adjusting the intervals between each lead 20 and the stem 10.

Table 2 shows test conditions of performance of the TO-CAN package in accordance with the first embodiment of the present invention. <Table 2>

The lead 20 exposed to air for receiving the electric signal is formed in the coaxial structure, and thus controlled to have a predetermined impedance (for example, 50Ω). Accordingly, an impedance in the stem 10 is matched to a predetermined value, and thus the impedances between the lead 20 exposed to air and the lead 20 existing in the stem 10 are matched, thereby removing reflection loss. Here, the g rounding conductor 60 has a thickness of 2mm. As far as the grounding conductor 60 is connected to the stem 10, the thickness of the grounding conductor 60 does not influence frequency properties of the RF feed line.

The impedance of the lead 20 inserted into the stem 10 has the predetermined value (for example, 50Ω).

The grounding conductor 61 has the same length as the lead 20 existing in the TO-CAN package 100, and the interval between the grounding conductor 61 and the lead 20 is 0.11mm. An impedance of the lead 20 existing in the TO-CAN package 100 has the predetermined value. As far as the grounding conductor 61 is adhered to the stem 10, the thickness of the grounding conductor 61 does not influence frequency properties of the TO-CAN package 100.

Figs. 5E and 5F are a w hole I eft s ide v iew and a w hole r ight s ide view illustrating the TO-CAN package in accordance with the present invention.

As illustrated in Fig. 5E, in the TO-CAN package 100, the RF feed lines 200 include the leads 20 for receiving the electric signals and DC lines 300 receive DC power. The w hole c ircumferences of the I eads 20 of the R F feed lines 200 for receiving the electric signals are covered with the glass layers 50, respectively, and the resulting circumferences thereof are covered with one grounding conductor 60. Referring to Fig. 5F, the leads 20 existing in the TO-CAN package 100 are partially covered with the grounding conductor 61 with the predetermined interval from the grounding conductor 61. As described above, as far as the g rounding conductors 60 a nd 61 are adhered to the stem 10, they do not influence the frequency properties of the

TO-CAN package 100, regardless of their thickness. Therefore, the grounding conductors 60 and 61 can also be formed in different shapes from Figs. 5E and 5F.

It can be identically applied to grounding conductors below. Figs. 6A and 6B are graphs showing reflection loss (| S11| ) and transmittance (I S21| ) of the TO-CAN package of Fig. 4, respectively. The graphs are measured when the grounding conductor 61 covers half of the whole circumference of the lead 20.

As shown in Fig. 6A, the reflection loss (I S11| ) of the TO-CAN package of Fig. 4 maintains 17dB to 30dB in the range of 1GHz to 10GHz. As compared with the reflection loss of the conventional TO-CAN package 1 maintaining 5.9dB to

34dB in the range of 1GHz to 10GHz, the reflection loss (| S11| ) of present invention is remarkably improved in 10GHz range.

As depicted in Fig. 6B, the transmittance (I S21| ) of the TO-CAN package of Fig. 4 maintains -O.OδdB to -0.5dB in the range of 1GHz to 10GHz. As compared with g eneral transmittance of -0.1 dB to 1.7dB, the t ransmittance (I S21| ) of the present invention is considerably improved. The 3dB frequency bandwidth reaches a few tens GHz.

As mentioned above, the conditions influencing the frequency properties of the TO-CAN package 100 relate to a thickness of the glass layer 50, a diameter of the opening 30 (namely, diameter of the material layer filled in the opening 30), and a diameter of the material layer (air layer 51 ) between the grounding conductor 60 and the lead 20.

Table 3 shows the ranges of the conditions for obtaining the properties of Figs. 6A and 6B in the first embodiment of the present invention.

Fig. 7 is a perspective view illustrating a TO-CAN package in accordance with a second embodiment of the present invention. The TO-CAN package 100 includes a stem 10 for receiving an optical device (not shown), an opening 30 (not shown) formed in a predetermined position of the stem 10, a lead 20 passing through the opening 30, a glass layer 42 (not shown) filled in the opening 30 for covering the lead 20, a grounding conductor 60 adhered to the surface of the stem 10 outside the TO-CAN package 100 and filled with a glass layer 31 , for covering the lead 20, and a grounding conductor 62 adhered overlapping with the surface of the stem 10 and the opening 30 inside the TO-CAN package 100, for covering part of the lead 20, an interval between the grounding conductor 62 and the lead 20 being filled with an air layer 51 (not shown). Figs. 8A to 8D are a plan view, a left side view, a right side view and a cross-sectional view (A-A') illustrating the TO-CAN package of Fig. 7, respectively.

Referring to Fig. 8A, the grounding conductor 62 covers part of the lead 20, and the interval between the grounding conductor 62 and the lead 20 is filled with the air layer 51.

As shown in Fig. 8B, the grounding conductor 60 covers the glass layer 50 covering the lead 20, and the grounding conductor 62 covers part of the lead 20 existing in the TO-CAN package 100 with the air layer 51 between the grounding conductor 62 and the lead 20. The grounding conductor 62 is adhered to the stem 10, overlapping with the stem 10 and the opening 30.

Fig. 8C illustrates the grounding conductor 62 adhered overlapping with the opening 30 of the stem 10.

As depicted in Fig. 8D, an RF feed line 200 (except the glass layer 42 in the opening 30) of the TO-CAN package 100 in accordance with the second embodiment of the invention has an insulation structure of the glass layer 50 - glass layer 42 - air layer 51. In addition, impedances are matched to a predetermined value in the whole RF feed line 200.

Table 4 shows test conditions of performance of the TO-CAN package in accordance with the second embodiment of the present invention. <Table 4>

The lead 20 exposed to air for receiving an electric signal is identical to that of the first embodiment of the invention.

A glass layer 41 is formed in the opening 30 so that an impedance of the lead 20 inserted into the stem 10 can have the predetermined value (for example, 50Ω).

The grounding conductor 62 has the same length as the lead 20 existing in the TO-CAN package 100, and the interval between the grounding conductor 62 and the lead 20 is 0.11 mm. An impedance of the lead 20 existing in the TO-CAN package 100 has the predetermined value.

Figs. 9A and 9B are graphs showing reflection loss (| S11| ) and transmittance (I S21| ) of the TO-CAN package of Fig. 7, respectively.

As shown in Fig. 9A, the reflection loss (I S11| ) of the TO-CAN package of

Fig. 7 maintains 17dB to 33dB in the range of 1GHz to 10GHz. As compared with the reflection loss of the conventional TO-CAN package 1 maintaining 5.9dB to

34dB in the range of 1GHz to 10GHz, the reflection loss (1 S11| ) of present invention is remarkably improved in 10GHz range. As depicted in Fig. 9B, the transmittance (I S21| ) of the TO-CAN package of Fig. 7 maintains -0.03dB to -0.3dB in the range of 1GHz to 10GHz. As compared with the transmittance of the conventional TO-CAN package 1 maintaining -0.1 dB to -1.7dB, the transmittance (| S21| ) of the present invention is considerably improved. The 3dB frequency bandwidth reaches a few tens GHz.

Table 5 shows the ranges of the conditions for obtaining the properties of Figs. 9A and 9B in the second embodiment of the present invention.

Fig. 10 is a perspective view illustrating a TO-CAN package in accordance with a third embodiment of the present invention. The TO-CAN package 100 includes a stem 10 for receiving an optical device (not shown), an opening 30 (not shown) formed in a predetermined position of the stem 10, a lead 20 passing through the opening 30, a glass layer 42 (not shown) filled in the opening 30 for covering the lead 20, a grounding conductor 60 adhered to the surface of the stem 10 outside the TO-CAN package 100 and filled with a glass layer 31, and a grounding conductor 63 adhered overlapping with the surface of the stem 10 and the opening 30 inside the TO-CAN package 100, for covering part of the lead 20, an interval between the grounding conductor 63 and the lead 20 being filled with a glass layer 52.

Figs. 11 A to 11 D are a plan view, a left side view, a right side view and a cross-sectional view (A-A') illustrating the TO-CAN package of Fig. 10, respectively.

Referring to Fig. 11 A, the semi-cylindrical grounding conductor 63 covers part of the lead 20, and the interval between the grounding conductor 63 and the lead 20 is filled with the glass layer 52. As shown in Fig. 11 B, the grounding conductor 60 covers the glass layer 50 covering the lead 20, and the grounding conductor 63 covers part of the lead 20 existing in the TO-CAN package 100 with the glass layer 52 between the grounding conductor 63 and the lead 20. The glass layer 52 indicated by a dotted line is positioned behind the glass layer 50. The grounding conductor 63 is adhered to the stem 10, overlapping with the stem 10 and the opening 30.

Fig. 11C illustrates the grounding conductor 63 adhered overlapping with the opening 30 of the stem 10, and the glass layer 52.

As depicted in Fig. 11 D, an RF feed line 200 (except the glass layer 42 in the opening 30) of the TO-CAN package 100 in accordance with the third embodiment of the invention has an insulation structure of the glass layer 50 - glass layer 42 - glass layer 52. In addition, impedances are matched to 50Ω in the whole RF feed line 200.

Table 6 shows test conditions of performance of the TO-CAN package in accordance with the third embodiment of the present invention. <Table 6>

The lead 20 inserted into the stem 1 0 i s identical to that of the second embodiment of the invention.

The interval between the grounding conductor 63 and the lead 20 existing in the TO-CAN package 100 is 0.26mm.

Figs. 12A and 12B are graphs showing reflection loss (| S11| ) and transmittance (I S21| ) of the TO-CAN package of Fig. 10, respectively.

As shown in Fig. 12A, the reflection loss (I S11| ) of the TO-CAN package of Fig. 10 maintains 17dB to 37dB in the range of 1 GHz to 10GHz. As compared with the reflection loss of the conventional TO-CAN package 1 maintaining 5.9dB to 34dB in the range of 1GHz to 10GHz, the reflection loss (| S11| ) of present invention is remarkably improved.

As depicted in Fig. 12B, the transmittance (I S21| ) of the TO-CAN package of Fig. 10 maintains -0.03dB to -0.3dB in the range of 1GHz to 10GHz. As compared with the transmittance of the conventional TO-CAN package 1 maintaining -0.1dB to -1.7dB, the transmittance (I S21| ) of the present invention is considerably improved. The 3dB frequency bandwidth reaches a few tens GHz.

Table 7 shows the ranges of the conditions for obtaining the properties of Figs. 12A and 12B in the third embodiment of the present invention.

Fig. 13 is a perspective view illustrating a TO-CAN package in accordance with a fourth embodiment of the present invention. The TO-CAN package 100 includes a stem 10 for receiving an optical device (not shown), an opening 30 (not shown) formed in a predetermined position of the stem 10, a lead 20 passing through the opening 30, a glass layer 42 (not shown) filled in the opening 30 for covering the lead 20, a grounding conductor 60 adhered to the surface of the stem 10 outside the TO-CAN package 100 and filled with a glass layer 32, and a grounding conductor 63 adhered overlapping with the surface of the stem 10 and the opening 30 in the TO-CAN package 100, for covering part of the lead 20, an interval between the grounding conductor 63 and the lead 20 being filled with an air layer 53.

Figs. 14A to 14D are a plan view, a left side view, a right side view and a cross-sectional view (A-A') illustrating the TO-CAN package of Fig. 13, respectively.

Referring to Fig. 14A, the grounding conductor 63 covers part of the lead 20, and the interval between the grounding conductor 63 and the lead 20 is filled with the air layer 53.

As shown in Figs. 14B and 14C, the grounding conductor 60 covers the air layer 32 (transparent, thus not shown) covering the lead 20, and the grounding conductor 63 covers part of the lead 20 existing in the TO-CAN package 100 with the air layer 53 (transparent, thus not shown) between the grounding conductor 63 and the lead 20. The grounding conductors 60 and 63 are adhered to the stem 10, overlapping with the stem 10 and the opening 30.

As depicted in Fig. 14D, an RF feed line 200 (except a glass layer 41 in the opening 30) of the TO-CAN package 100 in accordance with the fourth embodiment of the invention has an insulation structure of the air layer 32 - glass layer 42 - air layer 53. In addition, impedances are matched to a predetermined value in the whole RF feed line 200.

Table 8 shows test conditions of performance of the TO-CAN package in accordance with the fourth embodiment of the present invention. <Table 8>

The lead 20 inserted into the stem 10 is identical to that of the third embodiment of the invention. The interval between the grounding conductor 60 and the lead 20 existing outside the TO-CAN package 100 is 0.13mm, and the interval between the grounding conductor 63 and the lead 20 existing inside the TO-CAN package 100 is 0.11mm.

Table 9 shows the ranges of the conditions for obtaining the properties of the first to third embodiments of the invention in the fourth embodiment.

As described above, the grounding conductors 61, 62 and 63 of the

TO-CAN packages 00 in accordance with the first to fourth embodiments of the invention cover half of the circumferences of the leads 20 therein. Here, frequency properties when the grounding conductors 61, 62 and 63 differently cover the circumferences of the leads 20 will now be explained.

Figs. 15A to 15F are graphs showing reflection loss (1 S11| ) and transmittance (I S21| ) when the grounding conductors of the first to third embodiments differently cover the circumferences of the leads in the TO-CAN packages.

Figs. 15A and 15B are graphs showing reflection loss (| S11| ) and transmittance (I S21| ) when the grounding conductor 61 covers 1/4L, 1/2L and 3/4L of the circumference L of the lead 20 in the first embodiment of the TO-CAN package 100. As shown in Fig. 15A, the worst reflection loss (I S11| ) when the grounding conductor 61 covers 1/4L of the lead 20 is -15.32dB, and the worst reflection loss (I S11J ) when the grounding conductor 61 covers 3/4L of the lead 20 is -16.8dB, which are slightly different from the reflection loss when the grounding conductor 61 covers 1/2L of the lead 20. As illustrated in Fig. 15B, the transmittance (I S21| ) is almost identical, regardless of how much the lead 20 is covered.

As depicted in Fig. 15C, the worst reflection loss (| S11| ) when the grounding conductor 62 covers 1/4L of the lead 20 is -16.41dB, and the worst reflection loss (I S11| ) when the grounding conductor 62 covers 3/4L of the lead 20 is -17.545dB, which are slightly different from the reflection loss when the grounding conductor 62 covers 1/2L of the lead 20.

Referring to Fig. 15D, the transmittance (I S21| ) is almost identical, regardless of how much the lead 20 is covered.

As shown in Fig. 15E, the worst reflection loss (I S11| ) when the grounding conductor 63 covers 1/4L of the lead 20 is -17.74dB, and the worst reflection loss

(I S11| ) when the grounding conductor 63 covers 3/4L of the lead 20 is -17.72dB, which are slightly different from the reflection loss when the grounding conductor

63 covers 1/2L of the lead 20.

As illustrated in Fig. 15F, the transmittance (I S21| ) is almost identical, regardless of how much the lead 20 is covered.

As discussed earlier, when the grounding conductors 61 , 62 and 63 partially cover the leads 20 in the TO-CAN packages 100, the frequency properties of the invention can be obtained.

In accordance with the present invention, the method for manufacturing the RF feed line includes the steps of covering the lead 20 positioned outside the TO-CAN package 100 with a first insulation layer (glass layer 31 or air layer 32 described above) by a predetermined length to the opening 30 of the stem 10, and covering at least part of the circumference of the lead positioned inside the TO-CAN package 100 with a second insulation layer (air layer 51 or 53, or glass layer 52 described above).

The step for covering the lead 20 with the first insulation layer includes the steps of covering the lead 20 with the glass layer 31 or the air layer 32 by the predetermined length, and covering the glass layer 31 or the air layer 32 with the grounding conductor 60, and the step for covering the lead 20 with the second insulation layer includes the steps of covering the lead 20 with the air layer 51 or 53 or the glass layer 52, and covering part of the lead 20 with the grounding conductor 61 , 62 or 63 with the air layer 51 or 53 or the glass layer 52 between the grounding conductor 61 , 62 or 63 and the lead 20.

The method further includes a step for covering the lead 20 of the RF feed line 200 passing through the opening 30 of the stem 10 with a third insulation layer (air layer 41 or glass layer 42 described above).

In addition, the grounding conductor 61 , 62 or 63 covers half of the circumference of the lead 20 existing in the TO-CAN package 100.

As a result, in accordance with the present invention, the impedances of the whole RF feed line structure are matched as much as possible, the reflection loss (| S11| ) is i mproved to 17dB to 37dB i n the range of 1GHz to 10GHz, and the transmittance (l S2ll ) is improved to -0.03dB to -0.3dB in the range of 1GHz to 10GHz.

Moreover, the TO-CAN package for the 10Gbps high rate data transmission is obtained by improving the reflection loss and transmittance and allowing the stem and lead to have similar capacitances to the general structure.

Table 10 shows parasitic capacitances in the stems 10 in the first to third embodiments of the present invention.

Accordingly, the present invention embodies the module for transmitting lOGbps high rate data by considerably lowering a general parasitic capacitance value (0.46pF).

Although the preferred embodiments of the present invention have been described, it is understood that the present invention should not be limited to these preferred embodiments but various changes and modifications can be made by one skilled in the art within the spirit and scope of the present invention as hereinafter claimed.

Claims

What is claimed is:

1. A TO-CAN package for a lOGbps optical module including a stem for receiving an optical device, and a lead connected to the optical device through an opening of the stem, the package comprising an RF feed line having a first lead being covered with a first insulation layer by a predetermined length from the outside to the ingress of the opening of the stem, and existing outside the TO-CAN package, a second lead passing through and existing in the opening of the stem filled with a second insulation layer, and a third lead existing in the TO-CAN package, at least part of the circumference of which being covered with a third insulation layer by a predetermined length, the first to third leads being incorporated in a single body.

2. The TO-CAN package of claim 1 , wherein the second lead is covered with the second insulation layer.

3. The TO-CAN package of claim 1, wherein the first lead further comprises a first grounding conductor for covering the first insulation layer by the predetermined length.

4. The TO-CAN package of claim 1, wherein the third lead further comprises a second grounding conductor for covering the third insulation layer by the predetermined length.

5. The TO-CAN package of claim 4, wherein the second grounding conductor covers half of the circumference of the third lead with the third insulation layer between the second grounding conductor and the third lead.

6. The TO-CAN package of any one of claims 1 to 5, wherein the first insulation layer is a glass layer, the second insulation layer is an air layer, the third insulation layer is an air layer, and the second grounding conductor covers part of the circumference of the third lead with a predetermined interval from the third lead.

7. The TO-CAN package of any one of claims 1 to 5, wherein the first insulation layer is a glass layer, the second insulation layer is a glass layer, the third insulation layer is an air layer, and the second grounding conductor covers part of the circumference of the third lead with a predetermined interval from the third lead.

8. The TO-CAN package of any one of claims 1 to 5, wherein the first insulation layer is a glass layer, the second insulation layer is a glass layer, and the third insulation layer is a glass layer.

9. The TO-CAN package of any one of claims 1 to 5, wherein the first insulation layer is an air layer, the second insulation layer is a glass layer, the third insulation layer is an air layer, the first grounding conductor covers the circumference of the first lead by the predetermined length with a predetermined interval from the first lead, and the second grounding conductor covers part of the circumference of the third lead with a predetermined interval from the third lead.

10. The TO-CAN package of claim 1 , wherein an impedance of the first lead of the RF feed line is matched to a predetermined value with an impedance of the second lead and an impedance of the third lead.

11. An RF feed line for a TO-CAN package including a stem for receiving an optical device, and a lead connected to the optical device through an opening of the stem, the RF feed line comprising a first lead covered with a first insulation layer by a predetermined length from the outside to the ingress of the opening of the stem, and positioned outside the TO-CAN package, a second lead positioned inside t he opening of the stem, and a t hird I ead positioned i nside the TO-CAN package, at least part of the circumference of which being covered with a third insulation layer, the first to third leads being incorporated in a single body.

12. The RF feed line of claim 11 , wherein the first lead further comprises a first grounding conductor for covering the first insulation layer by the predetermined length.

13. The RF feed line of claim 11 , wherein the third lead further comprises a second grounding conductor for covering the third insulation layer by the predetermined length.

14. The RF feed line of claim 13, wherein the second grounding conductor covers h alf of the c ircumference of the third lead with the third insulation layer between the second grounding conductor and the third lead.

15. The RF feed line of any one of claims 11 to 14, wherein the first insulation layer is a glass layer, the third insulation layer is an air layer, and the second grounding conductor covers part of the circumference of the third lead with a predetermined interval from the third lead.

16. The RF feed line of any one of claims 11 to 14, wherein the first insulation layer is a glass layer, the third insulation layer is an air layer, and the second grounding conductor covers part of the circumference of the third lead with a predetermined interval from the third lead.

17. The RF feed line of any one of claims 11 to 14, wherein the first insulation layer is a glass layer, and the third insulation layer is a glass layer.

18. The RF feed line of any one of claims 11 to 14, wherein the first insulation I ayer i s a n air layer, the third i nsulation l ayer is an air I ayer, the first grounding conductor covers the circumference of the first lead by the predetermined length with a predetermined interval from the first lead, and the second grounding conductor covers part of the circumference of the third lead with a predetermined interval from the third lead.

19. The RF feed line of any one of claims 11 to 14, wherein the second lead is covered with the second insulation layer.

20. The RF feed line of claim 19, wherein the second insulation layer is one of an air layer and a glass layer.

21. A method for manufacturing an RF feed line for a TO-CAN package including a stem for receiving an optical device, and a lead connected to the optical device through an opening of the stem, the method comprising the steps of: ... covering a lead positioned outside the TO-CAN package with a first insulation layer by a predetermined length to the opening of the stem; and covering at least part of the circumference of a lead positioned inside the TO-CAN package with a second insulation layer.

22. The method of claim 21 , further comprising a step for covering the first insulation layer with a first grounding conductor by the predetermined length.

23. The method of claim 21 , further comprising a step for covering the second insulation layer with a second grounding conductor by the predetermined length.

24. The method of claim 23, wherein the second grounding conductor covers half of the circumference of the lead with the second insulation layer between the second grounding conductor and the lead.

25. The method of any one of claims 21 to 24, wherein the first insulation layer is a glass layer, the second insulation layer is an air layer, and the second grounding conductor covers part of the circumference of the lead with a predetermined interval from the lead.

26. The method of any one of claims 21 to 24, wherein the first insulation layer is a glass layer, the second insulation layer is an air layer, and the second grounding conductor covers part of the circumference of the lead with a predetermined interval from the lead.

27. The method of any one of claims 21 to 24, wherein the first insulation layer is a glass layer, and the second insulation layer is a glass layer.

28. The method of any one of claims 21 to 24, wherein the first insulation layer is an air layer, the second insulation layer is an air layer, the first grounding conductor covers the circumference of the lead by the predetermined length with a predetermined interval from the lead, and the second grounding conductor covers part of the circumference of the lead with a predetermined interval from the lead.

29. The method of any one of claims 21 to 24, further comprising a step for covering the lead positioned inside the opening of the stem with a third insulation layer.

30. The method of claim 29, wherein the third insulation layer is one of an air layer and a glass layer.