Why does a light cat use a single-mode optical fiber to send and receive data at the same time, but it uses two optical fiber transceivers?

Answer this question according to what I know.

Optical cat with a single optical fiber uses an optical transceiver with two optical fibers. An optical transceiver with a single optical fiber uses an sfp optical module with two optical fibers.

abstract

With the continuous development of optical transmission technology, a variety of transmission equipment and systems have emerged, each of which has different application occasions and applicable environments.

What do you think of single-core or double-core optical transmission? Please leave a message in the comments section to discuss.

If you need more help, please pay attention to it in private. thank you

Network geek, with a new perspective and new ideas, will accompany you to travel in the magical online world.

Not only optical cat devices can send and receive data through an optical fiber.

From the perspective of optical fiber resources occupied by transmission, optical fiber transceivers can also be divided into single-fiber and dual-fiber optical reception:

Double optical fiber light collection

The data transmission of dual-fiber optical receiver is earlier than that of single-fiber optical receiver.

Single fiber light collection

The technology of single fiber optical acquisition is later than that of double fiber optical acquisition, which saves optical fiber resources to some extent.

Single fiber optical receivers must be used in pairs, one end A and the other end B;

Single fiber optical receiver generally adopts SC interface.

Other extended reading

What other topics are you interested in about light collection?

Welcome to leave a message to discuss, like a little attention.

The operator's "light enters copper and retreats" scheme urges more network access to adopt optical fiber, so there are various uses of single fiber and double fiber in network access. Some netizens don't understand why they use it this way. Here is a brief explanation from three aspects.

Different access methods

Although they are all connected by optical fiber, the number of cores using optical fiber will be different with different access methods. Such as GPON, EPON and other PON network access, its network characteristics determine the use of a single optical fiber. PON access consists of three parts: OLT (local terminal), ODN (optical splitter) and ONT (customer terminal). Point-to-multipoint transmission, downlink broadcasting and uplink multiplexing save resources and investment. At present, PON access is widely used, and optical cat access is one of them.

Different application scenarios

In order to ensure the transmission quality and sufficient bandwidth, the core layer or convergence layer will adopt dual optical fiber access such as optical transceiver and optical module in terms of stability, security and reliability, and different optical fibers will be used for data transceiver to ensure that information transmission will not interfere with each other, thus ensuring normal communication between operators and customers and between devices. Therefore, dual fiber access will be used.

Different customer needs

At present, there are many network access devices and forms, and the equipment resources brought by customers when purchasing network equipment determine whether to use single fiber or double fiber. For example, the customer switch comes with FC dual-fiber optical module, and the enterprise uses LC single-fiber optical module to save investment, so the single and double use of optical fiber must be connected according to the actual situation of customers to meet the needs of customers.

I answer this question in combination with the network I use at home:

1. Now the network transmission architecture used at home is called pon technology. Pon is a passive optical network with point-to-multipoint structure. Pon consists of optical terminal olt, optical network single onu and passive optical splitter POS. See 1 for the topology diagram of passive optical network.

2. Why does the home bandwidth structure choose pon?

1) transmission distance is longer, and optical fiber transmission is adopted, and the access layer covers a radius of 20KM.

2) Higher bandwidth, 2.5G downlink per household, 1.25G uplink;

3) more optical fibers are saved, and the single optical fiber at the local end is led out to the residential optical fiber after being split, thus saving resources such as construction cost and optical fiber welding;

4) Triple play service, which supports the integration of bandwidth service, IPTV service, live broadcast and other services;

3. All cats in the family use one optical fiber to transmit and receive data. The basic principle is that pon adopts WDM technology to realize single fiber bidirectional transmission, that is, the transmitting end adopts the wavelength of 1490nm, and the receiving end adopts the wavelength of 13 10nm, that is, two frequencies in one optical fiber interfere with each other in transmission and reception, as shown in Figure 2.

4. There are also single-fiber transceivers and dual-fiber transceivers. A single optical fiber transceiver transmits signals with two different wavelengths in the same optical fiber. The transmission center wavelength of local single fiber optical port is 13 10nm, the reception center wavelength is 1550nm, and the transmission wavelength of remote single fiber optical port is 1550nm.

In the past, the older transceiver used two optical cables with the same wavelength 13 10. Nowadays, most new transceivers are single-core. Now there are also single-core optical modules. The principle of single-core transceiver is that the wavelength of receiving and transmitting light is different, so it should be divided into A end and B end and used in pairs. The A terminal emits light with the wavelength of 13 10 and receives light with the wavelength of 1550. The b terminals are 1550 and 13 10.

There is also an optical module of 13 10/ 1490.

This technology is what the network engineer tutorial says: wavelength division multiplexing.

Optical fiber is a nearly transparent transmission medium, as thin as hair, and the carrier of data is light. There are single-mode and dual-mode optical fibers, so there are naturally single-mode optical fiber transceivers and dual-mode optical fiber transceivers.

A single-mode fiber can be connected through a pair of single-mode fiber transceivers, which can send and receive signals at the same time, while a multimode fiber transceiver has two interfaces, which require a pair of multimode fibers to connect with a pair of multimode fiber transceivers, one multimode fiber is responsible for sending signals, and the other multimode fiber is responsible for receiving signals.

Difference between single-mode fiber and multimode fiber

Undoubtedly, the transmission of single-mode signals by single-mode fiber requires a thinner core, preferably 3~4 times the working wavelength. The optical signal is injected into the optical fiber at a specific incident angle, allowing only one direction of light to pass through. However, multimode fiber transmits multimode signals and has multiple transmission modes, allowing light to enter the fiber from multiple incident angles and propagate.

Single-mode fiber can only be transmitted in a single mode at a given working wavelength because of its small core, wide transmission frequency, small dispersion, larger transmission capacity and longer transmission distance. Multimode fiber is greatly affected by dispersion, so it has poor transmission performance, small transmission capacity and short transmission distance.

At this time, many friends will say, since single-mode fiber has so many advantages, let's simply use single-mode fiber to transmit. However, everything should consider the status quo. The core diameter of single-mode fiber is small, so it is difficult to control the beam transmission, and a laser is needed as the light source carrier. This kind of optical terminal is very expensive. The diameter of multimode fiber core is large, so LED can be used as light source.

Considering the cost, single-mode optical fiber is more suitable for long-distance data transmission (such as metropolitan area network and five-source optical fiber network). ); Multimode optical fiber is suitable for short-distance data transmission of about 300~400 meters, and is widely used in enterprise intranet, data center computer room and so on.

Optical fiber transmission principle

The principle of optical fiber transmission is actually very simple, that is, using the principle of total reflection in junior high school physics textbooks: when light enters the beam medium from the optical dense medium, the refracted light with a refraction angle greater than the incident angle will completely disappear, leaving only the emitted light.

Optical fiber is a fiber made of plastic or glass. The core of optical fiber is generally made of glass with high refractive index, and the surface layer is made of glass or plastic with low refractive index.

In this way, when light propagates in the fiber core at a certain incident angle, it will propagate along the zigzag propagation path, and this process is constantly total reflection.

Causes of optical signal propagation attenuation in optical fiber

When a beam of optical signal enters from one end of the optical fiber until it exits from the other end, the intensity of light will be weakened, which means that the propagation of optical signal in the optical fiber will also be attenuated. Optical power meter is usually used to measure the loss of optical fiber, where α represents the loss coefficient, which can be calculated by the length L of optical fiber, input power P 1 and output power P2.

The loss value of optical fiber directly affects the transmission distance and also determines the distance between optical fiber relay stations. The inherent characteristics, bending degree, extrusion, impurities, unevenness and butt joint of optical fiber may aggravate the attenuation of optical signal. In addition, the quality of the light source will also directly affect the generation distance of the optical signal.

Optical fiber is the blood of modern scientific and technological life.

Nowadays, home broadband, cross-county, inter-provincial and inter-city backbone networks, communication between mobile communication base stations and even network communication between countries are all using optical fibers. It can be said that optical fiber is equivalent to the blood of modern scientific and technological life. Without optical fiber, it is difficult for us to enjoy such a carefree surfing life.

The optical fiber has been received, and sending and receiving are separated. Single mode is a wavelength, so transmission and reception are separated. Multimode wavelength is different, just like two people speak English and one speaks Chinese. Then put it on the optical fiber. Listen to what you hear and say what you say. This can form the transmission of information.

Optical fiber transceiver also has an optical fiber to transmit and receive, and the wavelengths of uplink and downlink light are different and do not interfere with each other.

On this question, the questioner may be an entry-level network learner or a forward-looking transceiver who has never seen a single fiber core.

Household optical cats can be realized by using an optical fiber. This technology is realized by wavelength division multiplexing, that is, different services are transmitted by one optical fiber with different waveforms, which do not interfere with each other, and then converge from the transmitting end through a multiplexer and then couple to the optical fiber for transmission. At the time of receiving, optical carriers with various wavelengths are separated by demultiplexer, and then the optical receiver further processes them to recover the original signal, so that different services can be transmitted in the same optical fiber.

Similarly, if a single-tag transceiver wants to receive and transmit signal waves, it can't send or receive the same wavelength, otherwise it can't tell which one is sent and which one is received. Therefore, generally speaking, a single optical fiber transceiver is used in pairs, that is, the AB end is used for sending and receiving, and generally 13 10nm and 1550nm transceivers appear in pairs, so that different sending and receiving of different wavelengths in the same optical fiber can be distinguished. However, the dual-fiber transceiver does not solve the problem here, and can transmit and receive at one time with light waves of the same wavelength.

Previously, due to technical reasons, there were some problems in the implementation of single fiber transceiver, such as stability and familiarity with some network strings. I once encountered a problem, that is, QQ could not transmit files under single-fiber transceiver, but it worked immediately when it was replaced by dual-optical submersible transceiver. I didn't try different brands of transceivers at that time. Is it the transceiver or lan switches? But there is a problem in this respect.

With the development of technology, we basically use single fiber for data transmission, because single fiber is easier to deploy and saves resources.

Light cat is EPON or GPON, single fiber bidirectional; The optical fiber transceiver is Ethernet GE or XGE, and the dual optical fibers are bidirectional. The two are not a standard and cannot communicate with each other, so there are single fiber and double fiber.