Definition and Function of Optical Module
2019-09-25
Optical module is composed of optoelectronic devices, functional circuits and optical interfaces. The optoelectronic devices include transmitting and receiving parts. Simply put, the function of optical module is photoelectric conversion. The transmitter converts electrical signals into optical signals. After transmission through optical fibers, the receiver converts optical signals into electrical signals. The transmitting part is that the electric signal with a certain bit rate is input and processed by the internal driver chip to drive the laser diode (LD) or light emitting diode (LED) to emit the modulated optical signal with the corresponding rate. The internal part is equipped with an automatic control circuit of optical power, so that the output power of the optical signal is stable. The receiving part is: the optical signal input module with a certain bit rate is converted to electrical signal by the light detection diode, and the corresponding bit rate electrical signal is output by the preamplifier.
The transmitting part is that the electric signal with a certain bit rate is input and processed by the internal driver chip to drive the laser diode (LD) or light emitting diode (LED) to emit the modulated optical signal with the corresponding rate. The internal part is equipped with an automatic control circuit of optical power, so that the output power of the optical signal is stable. The receiving part is: the optical signal input module with a certain bit rate is converted to electrical signal by the light detection diode. After the preamplifier, the corresponding code rate electrical signal is output, and the output signal is generally PECL level. At the same time, when the input light power is less than a certain value, an alarm signal will be output. 3. Parameter and Significance of Optical Module. Optical modules have many important optoelectronic technical parameters, but for GBIC and SPF, the following three parameters are the most concerned when choosing them.
1) Central wavelength
At present, there are three main types of nanometer (nanometer) per unit:
850 nm (MM, multi-mode, low cost but short transmission distance, generally only 500 M); 1310 nm (SM, single-mode, large loss but small dispersion in the transmission process, generally used for transmission within 40 KM);
1550nm (SM, single mode, small loss but large dispersion in the transmission process, generally used for long-distance transmission over 40KM, the farthest direct transmission without relay 120KM);
2) Transmission rate
Bit per second, unit bps.
At present, there are four kinds commonly used: 155 Mbps, 1.25 Gbps, 2.5 Gbps, 10 Gbps and so on. The transmission rate is generally downward compatible, so 155M optical module is also called FE (100 mega) optical module, and 1.25G optical module is also called GE (giga) optical module, which is the most widely used module in optical transmission equipment. In addition, the transmission rate of SAN is 2 Gbps, 4 Gbps and 8 Gbps.
3) Transmission distance
Optical signal can be transmitted directly without relay amplification, per kilometer (also known as kilometer, km). Optical modules generally have the following specifications: multi-mode 550m, single-mode 15km, 40km, 80km and 120km, etc.
In addition to the above three main technical parameters (wavelength, speed, distance), the optical module has the following basic concepts, which need only a simple understanding.
A. Laser categorie
Laser is the core device of optical module, which injects current into semiconductor material and emits laser through photon oscillation and gain of resonator. At present, the most commonly used lasers are FP and DFB lasers. The difference between them is that semiconductor materials and resonator structures are different. The price of DFB lasers is much higher than that of FP lasers. FP lasers are commonly used in optical modules with transmission distance less than 40 KM, and DFB lasers are commonly used in optical modules with transmission distance greater than 40 KM.
B. Loss and Dispersion
Loss is the loss of light energy caused by absorption and scattering of medium and leakage when light propagates in optical fibers. This part of energy dissipates at a certain ratio with the increase of transmission distance. Dispersion is mainly caused by the different speed of electromagnetic waves of different wavelengths propagating in the same medium, resulting in different wavelength components of optical signals arriving at the receiving end at different times due to the accumulation of transmission distance, resulting in pulse broadening, and thus the signal value cannot be distinguished. These two parameters mainly affect the transmission distance of optical module. In practical application, the link loss of 1310nm optical module is generally calculated by 0.35dBm/km, while that of 1550nm optical module is generally calculated by. 20d/km. The calculation of dispersion value is very complex, and is generally only for reference.
C. Emission power and reception sensitivity
Emitting light power refers to the output light power of the light source at the transmitter end of the optical module. Receiving sensitivity refers to the minimum receiving light power of the optical module at a certain rate and bit error rate. The units of these two parameters are (meaning watt, the logarithmic form of power unit mw, the calculation formula is 10lg, and 1MW is converted to 0dBm). They are mainly used to define the transmission distance of the product. The transmission power and reception sensitivity of optical modules with different wavelengths, transmission rates and transmission distances will be different as long as transmission can be ensured. Distance will do.
D. Service life of optical module
International uniform standards, 7:10 24 hours uninterrupted work 50,000 hours (equivalent to 5 years). E. Optical fiber interface.
SFP optical module is LC interface, GBIC optical module is SC interface, and other interfaces are FC and ST.
Optical Module Classification
1. Classification by application
The application rate of Ethernet is 100Base, 1000Base and 10GE. SDH application rate: 155M, 622M, 2.5G, 10G.
2. Classification by package
According to the encapsulation points ; 9, SFF, SFP, GBIC, XENPAK, XFP.
1 & TImes; 9 package - welded optical module, the general speed is not higher than gigabit, mostly using SC interface.
SFF package - - welding small package optical module, the general speed is not higher than gigabit, mostly using LC interface.
GBIC package - Hot plug Gigabit Interface Optical Module, using SC interface.
SFP package - hot plug small package module, currently the highest rate of up to 4,000, mostly using LC interface.
XENPAK package - applied in 10,000 MHz Ethernet, using SC interface.
XFP package - 10G optical module, can be used in 10,000 Mega ethernet, SONET and other systems, mostly using LC interface.
The transmitting part is that the electric signal with a certain bit rate is input and processed by the internal driver chip to drive the laser diode (LD) or light emitting diode (LED) to emit the modulated optical signal with the corresponding rate. The internal part is equipped with an automatic control circuit of optical power, so that the output power of the optical signal is stable. The receiving part is: the optical signal input module with a certain bit rate is converted to electrical signal by the light detection diode. After the preamplifier, the corresponding code rate electrical signal is output, and the output signal is generally PECL level. At the same time, when the input light power is less than a certain value, an alarm signal will be output. 3. Parameter and Significance of Optical Module. Optical modules have many important optoelectronic technical parameters, but for GBIC and SPF, the following three parameters are the most concerned when choosing them.
1) Central wavelength
At present, there are three main types of nanometer (nanometer) per unit:
850 nm (MM, multi-mode, low cost but short transmission distance, generally only 500 M); 1310 nm (SM, single-mode, large loss but small dispersion in the transmission process, generally used for transmission within 40 KM);
1550nm (SM, single mode, small loss but large dispersion in the transmission process, generally used for long-distance transmission over 40KM, the farthest direct transmission without relay 120KM);
2) Transmission rate
Bit per second, unit bps.
At present, there are four kinds commonly used: 155 Mbps, 1.25 Gbps, 2.5 Gbps, 10 Gbps and so on. The transmission rate is generally downward compatible, so 155M optical module is also called FE (100 mega) optical module, and 1.25G optical module is also called GE (giga) optical module, which is the most widely used module in optical transmission equipment. In addition, the transmission rate of SAN is 2 Gbps, 4 Gbps and 8 Gbps.
3) Transmission distance
Optical signal can be transmitted directly without relay amplification, per kilometer (also known as kilometer, km). Optical modules generally have the following specifications: multi-mode 550m, single-mode 15km, 40km, 80km and 120km, etc.
In addition to the above three main technical parameters (wavelength, speed, distance), the optical module has the following basic concepts, which need only a simple understanding.
A. Laser categorie
Laser is the core device of optical module, which injects current into semiconductor material and emits laser through photon oscillation and gain of resonator. At present, the most commonly used lasers are FP and DFB lasers. The difference between them is that semiconductor materials and resonator structures are different. The price of DFB lasers is much higher than that of FP lasers. FP lasers are commonly used in optical modules with transmission distance less than 40 KM, and DFB lasers are commonly used in optical modules with transmission distance greater than 40 KM.
B. Loss and Dispersion
Loss is the loss of light energy caused by absorption and scattering of medium and leakage when light propagates in optical fibers. This part of energy dissipates at a certain ratio with the increase of transmission distance. Dispersion is mainly caused by the different speed of electromagnetic waves of different wavelengths propagating in the same medium, resulting in different wavelength components of optical signals arriving at the receiving end at different times due to the accumulation of transmission distance, resulting in pulse broadening, and thus the signal value cannot be distinguished. These two parameters mainly affect the transmission distance of optical module. In practical application, the link loss of 1310nm optical module is generally calculated by 0.35dBm/km, while that of 1550nm optical module is generally calculated by. 20d/km. The calculation of dispersion value is very complex, and is generally only for reference.
C. Emission power and reception sensitivity
Emitting light power refers to the output light power of the light source at the transmitter end of the optical module. Receiving sensitivity refers to the minimum receiving light power of the optical module at a certain rate and bit error rate. The units of these two parameters are (meaning watt, the logarithmic form of power unit mw, the calculation formula is 10lg, and 1MW is converted to 0dBm). They are mainly used to define the transmission distance of the product. The transmission power and reception sensitivity of optical modules with different wavelengths, transmission rates and transmission distances will be different as long as transmission can be ensured. Distance will do.
D. Service life of optical module
International uniform standards, 7:10 24 hours uninterrupted work 50,000 hours (equivalent to 5 years). E. Optical fiber interface.
SFP optical module is LC interface, GBIC optical module is SC interface, and other interfaces are FC and ST.
Optical Module Classification
1. Classification by application
The application rate of Ethernet is 100Base, 1000Base and 10GE. SDH application rate: 155M, 622M, 2.5G, 10G.
2. Classification by package
According to the encapsulation points ; 9, SFF, SFP, GBIC, XENPAK, XFP.
1 & TImes; 9 package - welded optical module, the general speed is not higher than gigabit, mostly using SC interface.
SFF package - - welding small package optical module, the general speed is not higher than gigabit, mostly using LC interface.
GBIC package - Hot plug Gigabit Interface Optical Module, using SC interface.
SFP package - hot plug small package module, currently the highest rate of up to 4,000, mostly using LC interface.
XENPAK package - applied in 10,000 MHz Ethernet, using SC interface.
XFP package - 10G optical module, can be used in 10,000 Mega ethernet, SONET and other systems, mostly using LC interface.
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