Related knowledge of bidi optical module

Bidi optical module: bidi --- bidirectional. It uses WDM technology to transmit and receive different central wavelengths in two directions, so as to realize the bidirectional transmission of optical signals by one fiber. Bidi modules must be used in pairs, and its biggest advantage is to save fiber resources. By tuning the diplexer to match the desired wavelength of transmitter and receiver, the bidirectional transmission of data is realized.

Application

Single fiber two-way is usually used in user access network to complete the communication of image, data and voice with low cost.

1. Single fiber bidi optical module is more expensive, but only one fiber is needed to save fiber resources, which is a better choice for users who are lack of fiber resources.

2. The dual fiber optical module does not need to be paired. Any two optical modules can be connected. The price is cheaper than that of single fiber bidi optical module, but one more fiber is needed. If the fiber resources are sufficient, the dual fiber optical module can be selected.

Working principle

The obvious difference between bidi optical module and traditional dual fiber bidirectional optical module is that bidi optical module is equipped with WDM coupler, also known as diplexer, which can couple and separate the data transmitted by a single fiber. Therefore, bidi optical module is also called WDM optical module.

In order to operate effectively, bidi optical modules must be used in pairs, and the operating wavelengths of the two diplexers must be complementary and consistent. For example, if there are two bidi optical modules used in pairs, namely a and B, the receiving wavelength of module a is the transmitting wavelength of module B, and the transmitting wavelength of module a is the receiving wavelength of module B.

Type of bidi optical module

(1) Bidi SFP optical modules: bidi SFP optical modules are usually used in high-performance integrated duplex data links through a single fiber. If the transmission distance is less than 40km, the wavelength scheme of bidi SFP optical module is 1310nm / 1550nm and 1310nm / 1490nm; if the transmission distance is more than 40km, the wavelength scheme of bidi SFP optical module is 1550nm / 1490nm.

(2) Bidi SFP + optical module: bidi SFP + optical module is an enhanced SFP optical module. It is used in the bidirectional 10g serial optical communication between 1330 / 1270nm transmitter and 1270 / 1330nm receiver, such as IEEE 802.3ae 10gbase-bx, with a transmission distance of 20km.

(3) Bidi x2 optical module: bidi x2 optical module is used in bidirectional 10g serial optical communication, and this optical module consists of two parts: the transmitter part uses 1330 / 1270nm DFB laser. The receiver uses integrated 1270 / 1330nm preamplifier and post amplifier.

(4) Bidi XFP optical module: bidi XFP optical module is an XFP MSA packaged optical module with built-in digital diagnosis function. Its emission wavelength and receiving wavelength are 1330nm / 1270nm and 1270nm / 1330nm respectively. It is generally used with banded SMF, and the maximum transmission distance can reach 10km. In addition, the power consumption of 2G optical module is less than that of 10G Optical module.

Why choose bidi optical module?

The most obvious advantage of bidi optical module is that it can reduce the number of ports on the fiber patch panel, save the cost of fiber cabling infrastructure, reduce the cabling space, help fiber management, and reduce the number of optical fibers required. The price of bidi optical module is higher than that of traditional dual fiber bidirectional optical module, but the number of optical fibers required by bidi optical module per unit transmission distance is reduced by half. For many network lines, the cost savings of using fewer fibers far outweigh the cost of purchasing bidi optical modules.

The difference between single fiber bidirectional optical module and double fiber bidirectional optical module:

1. WDM technology is adopted in single fiber bidirectional optical module, but double fiber bidirectional optical module is not used;

2. The single fiber bidirectional optical module needs to be used in pairs, and the double fiber bidirectional optical module does not need;

3. The structure of single fiber bidirectional optical module is more complex than that of double fiber bidirectional optical module, and a splitter is needed in the optical module;

4. Only one fiber is needed between single fiber bidirectional optical modules, and two fiber bidirectional optical modules are required;

5. Generally speaking, the price of single-mode optical module is higher than that of multi-mode optical module, and the reasons are as follows:

The core diameter of single-mode fiber is small, only one mode transmission is allowed, the dispersion is small, and the coupling with optical devices is relatively difficult; the core diameter of multi-mode fiber is large, allowing hundreds of mode transmission, so the coupling with optical devices is relatively easy, and the size of coupling components is well matched with multimode fiber; Single mode optical module can run on both single-mode fiber and multimode fiber, while multimode optical module can only operate on multimode fiber.

Introduction of common optical modules for SFPs

At present, the highest speed is up to 10.3G, and the interface is LC. It is composed of laser (including transmitter Tosa and receiver Rosa), circuit board IC and external accessories. The external accessories include shell, base, pcba, pull ring, clasp, unlocking part and rubber plug.

Classification of optical modules for SFPs

① According to the rate, there are 155m / 622m / 1.25g/2.125g/4.25g/8g/10g, of which 155m and 1.25g are widely used in the market;

② According to the wavelength: 850nm / 1310nm / 1550nm / 1490nm / 1530nm / 1610nm, the wavelength is 850nm, it is a multi-mode SFP, the transmission distance is less than 2km, the wavelength is 1310 / 1550nm, the transmission distance is more than 2km, the price of these three wavelengths is relatively cheaper than other wavelengths;

③ According to the distance, there are short distance, medium distance and long distance;

④ According to the transmission mode: electrical port, single-mode, multi-mode;

⑤ The special types of SFPs include bidi-sfp, electrical port SFPs, cwdmsfp, dwdmsfp, and SFP + optical modules.

Differences between SFPs and bidi SFPs

As we all know, a common SFP module usually has two ports, one is TX port for transmitting signals, the other is RX port for receiving signals. Different from the common SFP module, bidi SFP module has only one port, which is filtered by the filter in the optical module. The integrated WDM coupler is used to transmit and receive signals on a single fiber. At the same time, 1310nm optical signal is transmitted and 1550nm optical signal is received, or vice versa.