RU2537510C2 - Method for connection between electronic modules for transmitting optical signals - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: invention relates to communication engineering and can be used in optical communication systems. A method, where the housing of electronic modules is connected directly using a key which is made in advance and installed such that corresponding optical windows thereof which are pre-arranged flush with external surfaces which are made with given flatness and roughness parameters coincide with a given accuracy.

EFFECT: wider range of methods of solving miniaturisation tasks in microelectronics.

6 dwg

Description

The invention relates to microelectronics - the electronics section.

“At the beginning of the 21st century, a serious technical problem escalated in electronics, which is called the“ tyranny of interconnects. ”<...> All the fruits of miniaturization began to eat up interconnects” ().

The present invention proposes one way to solve or reduce the severity of this problem.

The technical result of the invention is the expansion of the arsenal of methods for solving the problem of miniaturization in microelectronics.

Consider such a part of the interconnects as the connectors, and the connectors are optical, and we will consider the connection between the electronic modules.

“Optical plug connectors (OPC) have the same purpose in fiber-optic communication lines (FOCL) as electrical connectors (ER) in electrical communication lines. The only difference is that the optical connectors ensure the continuity of the optical, and not the electric flow. The first PRs appeared simultaneously with optical cables (OK), much later than the ER ”(from elc.com/index.php?option=com content & view = article & id = 120: opticheskie-razemy & catid = 44: 2011-03-01-13- 53-39 & Itemid = 1).

“The optical connector consists of a shell, inside of which there is a ceramic tip (ferul) with a precision longitudinal concentric channel. The most common external diameter of a ferul is 2.5 mm, but ferrules with a diameter of 1.25 mm are used in optical connectors with a small form factor.

The ferul is connected to the optical fiber: a piece of fiber without a sheath is inserted into the channel of the tip and fixed, the protruding end of the fiber is chipped parallel to the surface of the end of the ferul, the end of the ferul is polished. Next, the ferrule with the fiber is combined with the connector body. After combining the fiber and ferul, the build quality is tested for defects (for example, on a microscope and interferometer). For single-mode fiber, the alignment accuracy should be higher than 0.1 μm, the angular deviation is not more than 5 degrees, and the return loss is not less than 40 dB ”(information from opt taken from the site).

“The purpose of the optical connector is to ensure the passage of light from one fiber optic element to another with the lowest possible optical loss at the junction formed by the connector.

The complexity of minimizing losses at the junction is primarily due to the need to center the cross section of the transmitting and receiving OBs in the connector, which must be performed with high accuracy, since the diameter of the OB is small - 50 and 62.5 μm for multimode (MM) and 10 μm for single-mode (OM) fibers. This centering is carried out using a ferrule tip.

The optical connector should provide minimal insertion loss (interface parameter) both in normal climatic conditions and when exposed to various external factors. In addition, the stability of the joint parameters during repeated connection-disconnection should be guaranteed.

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The main characteristics of optical connectors include: transmission parameters, long-term stability and resistance to external conditions.

The main parameters of the transmission of OR are insertion loss and back reflection. These parameters depend mainly on factors such as the lateral displacement of the axes and the angle between them, as well as on the Fresnel reflection of the optical signal at the interface between two optical media.

Optical attenuation has a major effect on the total loss in the optical path. The magnitude of the optical attenuation mainly depends on the lateral deflection of the cores of the joined optical fibers.

Another important optical characteristic is back reflection. The main source of the reflected signal is the interface between two media, for example, the material of the optical fiber and air. This component of losses can reach significant values. In addition, the reverse reflection is variable over time. Under the influence of external influences, it can violate the stability of the system. The most serious problems are the reverse reflection for narrow-band lasers with high radiation coherence (which, for example, are used in DWDM systems and equipment for cable television networks).

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The main types of optical connectors:

ST - single connector. Small in size with a bayonet lock for fixing (the nut needs to be turned and connected by a quarter turn - 90 °). This type of connector is preferably used where vibration protection is not required, such as in an office. Recommended for use in multimode connections. The mounting technology of these connectors is glue or crimp. Not recommended for new installations.

FC - a single connector having a metal or plastic housing and secured by a threaded connection. Most commonly used with single-mode fibers and has an insertion loss level of about 0.4 dB. Resistant to shock and vibration. Recommended for single-mode connections in long-distance radio systems and specialized systems. The threaded connection used in the connectors provides reliable protection against accidental disconnection.

SC is the most popular type of optical connector made from plastic with a rectangular cross section. Fixing is carried out by a latch with a latch on the principle of "push-push", which provides protection against accidental mechanical influences. Due to their shape and principle of operation, these connectors can be installed in switchgears with a high density of installation. The advantages of the connector type SC are the ease and speed of connection due to the absence of rotational movements during its implementation. Also, unlike a single (simplex) connector, a double (duplex) connector is used, in which two SC connectors are combined into one housing. Installation technology - glue or crimp. The insertion loss of the SC optical connector is 0.4 dB or less.

SMA is a small connector with a locking nut that provides a rigid connection. It used to be used in communication devices for transmitting data in measuring equipment. In addition to LAN and SCS, this type of connector is widely used in industrial systems, medical and military equipment. Due to the use of special design measures, the degree of protection of spliced fibers can be IP-65.

LC - Miniature connectors that are approximately two times smaller than conventional SC, FC, ST, with a tip diameter of 1.25 mm rather than 2.5 mm. This allows you to realize greater density when installed on the patch panel and a dense installation scheme in the rack. The connector is fixed using a clamping mechanism that eliminates accidental disconnection.

D4 - This type of optical connector is widely used for single mode fiber. It looks a lot like the FC connector, but it has a smaller diameter tip - 2.0 mm. The insertion loss of the D4 connector is about 0.4 dB.

FDDI - The connector is designed as a two-channel, uses two ceramic tips and a side latch mechanism. A durable casing protects the tips from accidental damage, and a floating joint provides it with a tight joint without effort. The insertion loss level is about 0.3 dB for a single-mode fiber and about 0.5 dB for a multimode. FDDI is the LAN technology used

for packet data at a speed of 100 Mbps in accordance with the ANSI standard.

E-2000 and F-3000 connectors. To disconnect the connectors, a special key is required, so the probability of accidentally disconnecting the E-2000 connector is reduced to zero. After disconnecting the connector, the hole is closed with special curtains. These connectors are distinguished by a large number of connection cycles - up to 2000.

There are many more types of optical connectors —HDSC, FJ, Mini-MPO, SC-Compact, MU, SCDC, SCQC, Mini-MT, MT-RJ, Optoclip II, VF-45, etc. These connectors have a narrow application purpose and have not received widespread use now ”(from http://partner-elc.com/index.php?option=com content & view = article & id ^: = 120: opticheskie-razemy & catid = 44: 2011-03-01-13-53-39 & Itemid = l).

Enclosures in existing optical connectors limit miniaturization.

It is proposed to get rid of these cases by switching to the direct contact of the electronic modules in such a way that their optical windows, which are flush with the external surfaces, are in direct contact.

An optical window is a structural optical element intended for the entry / exit of optical radiation into an optical system. Typically, an optical window is a plane-parallel plate (GOST 1121-75 Plane-parallel glass plates. Sets. Specifications). However, it can also be L-shaped.

The optical window (protective glass) is fastened in the proposed method by gluing into the module case, in which a through hole of the corresponding shape and size is prepared (http://ru-auto./pics/204188302350006/). This mounting method allows you to position the optical window flush with the outer surface of the electronic module.

The requirement for any optical connector is “to ensure the passage of light from one fiber optic element to another with the lowest possible optical loss at the junction formed by the connector” (ibid.). Since the role of the optical connector in this case is played by the electronic modules themselves - for this purpose, the surfaces of the electronic modules that must be in contact are performed with the given parameters of flatness (tolerances according to GOST 24643-81) and roughness (see GOST 2789-73). The coincidence of the corresponding windows with a given accuracy is achieved using the key.

“With regard to the connectors, the key means the presence of various protrusions or recesses that allow the only correct connection of the pin and socket”

(http: // \ vww.hyperline.rii / catalog / jacks /). The word “key” has the same meaning here, if we replace “connectors”, “pin” and “socket” with “electronic module housings”. After replacement, it turns out: Applied to

electronic modules, the key means the presence of various protrusions or recesses that allow the only correct connection of electronic modules. These protrusions and grooves using well-known technologies, for example, stamping and casting, can be made in the right quantity and any size and placed in different places of the electronic modules, ensuring their unambiguous joining. The group of electronic modules formed after such a docking is fixed and included in the corresponding equipment, as well as one electronic module. Due to the extreme simplicity of this process, it is not shown in the figures.

In FIG. 1-3 shows examples of various types of electronic windows and their location (Fig. 1 - optical windows of rectangular 2 and square 3 shapes on the side surface of the housing of the electronic module 1; Fig. 2 - two rows of round optical windows 4 on the side surface of the housing of the electronic module 1 Fig. 3 - optical windows 5 simultaneously on the upper and side surfaces of the housing of the electronic module 1).

FIG. 4-6 illustrate examples of methods for delivering an optical information signal to an optical window (optical windows) inside an electronic module.

In FIG. 4 shows the structure of a high-density electronic module that does not have air cavities. Here 1 is the case of the electronic module, 6 is the optical window, 7 is the substrate, 8 is the integrated optical waveguide, 9 is the dielectric filler, 10 is the protective layer of the polymer. A "track" made of polymer - an integrated (in one of the layers of the printed circuit board) optical waveguide 8 (for example, SU-8) - is connected directly to the optical element - optical window 6.

In FIG. 5 shows the structure of the electronic module, the optical system of the information channel of which has a matching optical element - microlens 12, whose task is to match the aperture of the beam at the output of the integrated optical waveguide 8 and the size of the optical window 6. It also shows the case of the electronic module 1, substrate 7 and a fixing layer of polymer 11.

In FIG. 6 shows a diagram in which standard optical waveguides 13 are used as optical channels, which transmit the signal (s) to the optical windows 6. The connection of the waveguide can be either by optical welding or by means of an optical polymer with a corresponding refractive index. In the same way, the signals inside the electronic module can transmit from the optical window 6.

It is clear that the transition from the known optical connectors to the non-detachable (in the usual sense) connection of electronic modules is a step towards further miniaturization of electronic equipment.

Claims (1)

The method of connection between electronic modules for transmitting optical signals, namely, that the housings of electronic modules are connected directly using a key so that their respective optical windows, which are pre-flush with external surfaces that perform with the given parameters of flatness and roughness, coincide with given accuracy.

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