Why should optical fiber telephone be installed in underground utility tunnel?

Why should optical fiber telephone be installed in underground utility tunnel?

Application significance of fiber phone in pipe gallery

1、 Normative interpretation

It is stipulated in GB 50838-2015 that the fixed communication system should be set up in the pipe gallery, and there are no special requirements on the performance requirements. It seems to be a dispensable device. Because of the special structure form of the pipe gallery with long transmission distance and the ordinary analog telephone can not solve the communication in the pipe gallery, the optical fiber transmission mode is mostly adopted, so most of the owners carry the sound It is not worth spending so much money on such a dispensable product. Therefore, when purchasing products, they mostly choose a low-cost product in order to respond to the requirements of the national standard, pay no attention to the quality and performance of the product, only to solve the problem of "whether there is one". But what is the actual situation?

After two years' visit, 800 Smart has visited hundreds of owners, operation and maintenance units and major design institutes of pipe gallery, and accumulated some opinions on the application of fixed communication system in pipe gallery and some necessary functions of pipe rack communication system for your reference.

2、 Pipe gallery telephone is indispensable

In the normal operation of the pipe rack, the telephone in the pipe gallery is indeed a dispensable existence. Although the system can communicate with the external public network, no one is willing to chat with friends on the phone in the pipe gallery. Only in very few cases can the operation and maintenance personnel communicate with the outside world through the fixed line system.

But this is in the normal operation state, however, the pipe gallery will not always be in the normal operation state, if so, the pipe gallery will lose its significance of existence - to solve the problem of urban road zipper.

Due to the repair and maintenance of the pipelines entering the gallery, the maintenance of the pipe gallery itself and other reasons, there will be a large number of professionals working in the gallery in addition to their own operation and maintenance personnel.

There is no mobile phone signal coverage in the pipe gallery, so the fixed line communication system becomes the only external communication system for these temporary corridor entry personnel, and it is the communication guarantee system for them to complete their work and provide efficiency.

At the same time, with the increase of the length of the pipe gallery and the increase of the types of pipelines entering the gallery, more and more temporary workers will enter the gallery. Because of this, the dependence on the communication security system in the pipe gallery will become stronger and stronger

Therefore, the fixed telephone communication system in the pipe gallery is not a dispensable system or an emergency telephone dispatching system, but an important communication guarantee system related to the operation and maintenance efficiency of the pipe gallery.

3、 Application requirements of fiber phone in pipe gallery

In GB 50838-2015, there is only a simple description of the fixed communication system, including the location of telephone installation, distance between telephones, signal connection mode, etc. as a minimum standard for project construction, such requirements only solve the problem of "whether there is one". Since the fixed communication system plays such an important role in the pipe gallery, the fixed line system is not simply a question of "whether there is" but "whether it can be used". To solve the problem of "whether it can be used", the author thinks that we should consider the following aspects.

1. According to the characteristics of long transmission distance of pipe gallery, optical fiber transmission mode should be adopted, which has been agreed by major design institutes and owners, so no further explanation is given here.

2. According to the characteristics of constant temperature and constant humidity in the pipe gallery, all electrical products entering the gallery must have a protection grade of no less than IP65, which is determined by the characteristics of constant temperature and constant humidity of the pipe gallery. There are many microorganisms growing in the pipe gallery, and the corrosion of these microorganisms to electronic components will be very serious. Therefore, the electrical equipment entering the gallery needs to have a very good protection grade, and the national standard requires that it shall not be lower than IP The author thinks that IP67 will be more suitable for the use of pipe rack, because the moisture is all-round surrounding the equipment, IP65 is waterproof splash, IP67 is waterproof immersion. For electrical equipment working in the environment of pipe rack for a long time, waterproof immersion will have better protection effect on the equipment, and can also make the service life of the equipment longer. During the visit, the author found that there are two kinds of equipment damaged in the pipe gallery due to insufficient protection level. One is the telephone in the pipe gallery, and the other is the camera. Many owners are greedy for low price when purchasing, and use the equipment with insufficient protection level, which causes great trouble to the follow-up work.

3. As a communication security system, it is also an emergency telephone system, so the system must have the function of one button call.

4. As a set of communication guarantee system, the system should be able to communicate with the external public network. Not only can the telephone in the pipe gallery be called out, but also the telephone users of the external public network can call in the pipe gallery, and make sure that any call in the pipe gallery will not affect the use of other phones, so as to realize the real communication without blocking.

5. As a set of communication guarantee system, the system should make every telephone in the system in good condition, so how to ensure that hundreds or even thousands of telephones are easy to use? If maintenance is done manually, it is unrealistic to observe whether each phone can be used or not, because the appearance of the phone can not tell whether it is easy to use or not. In this way, it is necessary for the fixed line communication system to monitor its terminals and intermediate connection equipment, so that when any component of the system, including but not limited to switches, optical fiber transceivers, optical terminals, telephones, etc., fails, it is necessary to get feedback at the first time and report it to the operation and maintenance personnel Carry out maintenance. This is what we often say that the system should have the function of self-test.

6. It is not enough for the communication support system to have self-test function. No matter what kind of networking mode of the system, considering the structure of the pipe rack, most of them adopt the cascade mode. Any connecting equipment in the middle will provide transmission signals to the next connected equipment. In this way, once one of the intermediate equipment fails, all the equipment in the future will not be able to use, The whole communication system collapsed. In order to prevent the occurrence of this situation, the system should have a self-healing network. The self-healing here does not mean that the equipment can be repaired by itself when it is broken, but that if a point in the network fails, the whole network can still be used by using technical means, and the network can not be collapsed or paralyzed due to a little fault. At present, there are two ways to realize self-healing. One is to adopt the mode of fiber-optic self-healing switch, which will automatically short-circuit the switch to ensure the use of the network in case of failure; the other is to adopt the mode of fiber-optic self-healing ring, which uses both sides of optical transmission to bypass the fault point to ensure the use of the network.

7. As a communication system, it should also have recording function to provide basis for investigation and evidence collection in case of emergency in pipe gallery.

8. At present, many pipe racks are designed with gas silos. It is clearly stipulated in GB 50838-2015 that the gas storage belongs to class II explosion-proof places. Then the electrical equipment in the gas warehouse needs to have explosion-proof qualification, including the telephone in the fixed telephone communication system, and must have the effective explosion-proof qualification issued by the National Laboratory. As for intrinsic safety or flame-proof, as long as the explosion-proof requirements of class II places are met That's fine.

Composition requirements of optical fiber telephone system

1、 Safety -- see the protection level

The humid environment of the pipe gallery determines that the optical fiber telephone extension in the pipe gallery must have very good sealing performance. At present, the major design institutes basically require that the protection grade of the extension should be IP65 or above, but once the water enters the pipe gallery, all the units will be scrapped. Just imagine that after the pipe gallery is flooded, all the units entering the gallery will send personnel to the gallery for emergency maintenance. At this time, a complete set of communication system will help the whole emergency repair work. The communication equipment with IP67 protection grade can keep the equipment in good working performance even after being immersed in water. Therefore, whether the communication equipment of underground pipe gallery has the protection of IP67 The level of care is crucial. At the same time, the corrosion products such as moisture and various microorganisms are widespread in the pipe gallery, which seriously corrodes the equipment. The pipe gallery extension unit with high protection level will certainly better protect the circuit in the machine, and will objectively play a role in extending the service life of the unit in the pipe gallery.

2、 Anti interference -- look at "all fiber" access mode

The humid environment of the pipe gallery and the harmful gas such as biogas generated by itself are seriously harmful to human life. In order to ensure the safety of the operation and maintenance personnel, all kinds of ventilation equipment in the pipe gallery will be opened or normally opened from time to time. The operation of these ventilation and exhaust equipment (mainly motor) will produce complex electromagnetic interference, which will inevitably interfere with the telephone signal of the pipe gallery. At present, the only way to solve this interference is to use all optical fiber access, but here we should emphasize "all fiber" -- no matter the extension or the auxiliary machine all use optical fiber connection.

At present, some manufacturers have also proposed the concept of all fiber access, but in fact, only optical fiber connection is used for the trunk road, and cable connection is used between the auxiliary unit and the extension unit. At this time, it should be noted that the cable attenuation in the humid environment in the pipe gallery is very serious, which will inevitably lead to the system failure rate is particularly high, and the maintenance is complex, and the cable needs to be replaced within a few years , which brings huge workload. Since most of the owners of the pipe gallery are PPP mode owners, and most of the operation time is between 20-25 years, then in the whole life cycle of the communication system, the largest reduction of maintenance will also bring considerable profit margin for the owners.

3、 Function convenience: is the incoming and outgoing unblocked

The construction location of the pipe gallery determines that mobile phones can not be used here. Then the optical fiber telephone in the pipe gallery is the only tool for external communication. It should be used as a communication guarantee system. This determines that the optical fiber telephone in the pipe gallery can not be equal to other industrial phones or emergency phones. The optical fiber telephone sets in the pipe gallery should not only realize the automation of each extension and the center in the corridor In addition, the free communication between the public and the outside world can also be ensured by the free communication between the public and the outside world in normal times.

One thing to note here is that some manufacturers only mention the external call function of their products, but they don't mention the number of external lines that can be connected to their system at the same time, because most of the corridor entry units will have several or more than a dozen. In addition, considering the special situation of emergency rescue and disaster relief, 1, 2 or 3, Four external lines are obviously not enough. In particular, in some star connection schemes, the main unit and the auxiliary machine are completely a telephone. The function of the auxiliary machine is to extend the handset, microphone and dial-up keyboard of the host computer. The main and auxiliary computers use a signal source. In this way, if any telephone is in conversation, other calls can not be used, and the calls from outside can only be answered on the host computer, and the auxiliary machine is to answer No phone calls. These need to be paid close attention by the users of pipe gallery when purchasing.

4、 System stability - can the system self check and self heal

Considering the large number of fiber-optic telephone sets in tube Gallery, how to ensure its security and stability, self-healing ring function and self-test function are particularly important. This function will quickly remove the fault in case of failure, avoid system crash, and provide convenience for the expansion of communication equipment after the extension of pipe gallery. By the way, most of the pipe racks belong to the test section pipe gallery. The length of the pipe gallery is relatively short, and the number of telephones is not large. IP phone, under the banner of optical fiber telephone, can attract the attention of many purchasers by virtue of the price advantage, and it can really meet the needs of the pipe gallery at the present stage. However, with the expansion of the pipe gallery in the future, the center of the IP phone scheme will be set up With the increase of the number of telephones, the complexity of the system, the instability of the system and the high maintenance cost will bring disastrous consequences to the owner or the operator of the pipe rack.

Finally, it should be emphasized that according to the characteristics of different functional compartments in the pipe gallery, the selection of optical fiber telephone is also different. In the gas cabin, explosion-proof optical fiber telephone must be selected, and it must also be independent and connected with other cabins. This requirement is clearly specified in article 5.4.7 of national standard GB 50838-2015.

At present, the optical fiber telephone of the pipe gallery has become the necessary supporting equipment for the construction of the pipe gallery. However, few fiber-optic communication systems can really realize the above functions and guarantee. Some bad manufacturers still use the original IP telephone or emergency industrial telephone mode under the banner of fiber-optic telephone. Therefore, we must have a clear understanding of the system and pay attention to it Whether it meets the national standard.