Bai Lei suddenly wanted to cry even more, why is the gap between this person so big, Teacher Chang shouldn't be a beautiful little girl. Pen & Fun & Pavilion www.biquge.info

Chen Yue also sighed, people are really angry compared to people.

This is definitely the first time Chang Qing has said such kind words at a weekly meeting.

"Zhuo Ling, let's talk about it next. ”

It's full of encouragement.

"Teachers, seniors, good evening, I am Zhuo Ling, the first report, if there is any omission, please criticize and correct, my research topic is the mitigation and compensation technology of optical fiber polarization mode dispersion, PMD is one of the main obstacles hindering the long-distance propagation of high-speed optical fiber communication, due to the statistical characteristics of PMD, it is quite difficult to recover the transmission signal damage caused by PMD, my work is to summarize the current commonly used PMD mitigation technology, photoelectric compensation technology status...... In addition, the compensator structure, feedback signal extraction and particle swarm optimization control algorithm in PMD optical domain compensation technology are preliminarily understood. ”

"It's very good, I'm just getting in touch with the subject, and my professional foundation is still very weak to do this, it's not easy, let's go on. Chang Qing said with a smile, it was simply incarnated as Maitreya Buddha.

The other students can only sigh, it seems that Zhuo Ling can enter the laboratory in her sophomore year, not without reason, how to do it, you have to listen to it to know.

Guan Debao has always been unhappy in his heart, he can't vent his anger, he looked at Zhuo Ling with cold eyes, and made up his mind, no matter what she said, he must let her know that she is terrible and has encountered some setbacks.

"High-speed optical fiber communication network has become the direction of development, and the dispersion chromaticity, polarization touch dispersion, and nonlinear effect in the optical fiber have become the main factors limiting the further growth of the transmission rate of the optical fiber communication system. ”

Chang Qing interrupted: "Let me compensate, as the top OFC/NFOEC conference for the development of optical fiber communication, the articles on PMD have remained high in recent years, about 36 in 01, and more than 50 in 02, which is a research hotspot, and the topics of our laboratory have always been at the forefront." ”

As soon as these words came out, not only the students of other teachers, but also Bai Lei were very jealous, it was obvious that the research value of PMD was higher than his dispersion chroma, why! Give such a good topic to a sophomore girl, because the subject matter is new, it is obviously easier to produce results, and the opportunity to choose a famous foreign school is also greater.

Zhuo Ling continued: "In an ideal single-mode optical fiber, the interface is ideally circular, but in practice, due to the imperfection of the manufacturing process, the cross-section is elliptical, there is stress inside, or the fiber is bent, and it is also affected by ambient temperature, electromagnetic field, and vibration, which makes the parallel mode HE1 and HE2 degenerate, resulting in different propagation constants. ”

Chang Qing wrote a line in his notebook, and then quietly pushed it in front of Liu Chen, "I took care of it just right, take me to drink the best tea tomorrow, the gluttony is hooked, it's really uncomfortable." ”

Faint, this care is too obvious! Liu Chen was a little speechless.

Chang Qingdu said it so obviously, other teachers will naturally not be embarrassed, and I think that the sophomore girl can do this step in a short time is indeed worthy of recognition, after all, it is not easy to fully understand a few English literature, let alone a comprehensive analysis, which requires talent and a lot of time to focus.

Guan Debao couldn't wait any longer, and directly interrupted: "We all know that due to the difference in the refractive index between the fast and slow axes, when the light is transmitted in the birefringent fiber, the component transmission speed on the fast and slow axes is different, which ultimately causes the optical pulse at the output end to be broadened or split, which is the so-called polarization mode dispersion, and the index is the PMD coefficient, which should be less than how much?"

"At present, the accepted parameter setting is 0.5 ps and the number of km, and sometimes the limit is set to 0.8. ”

"What factors are related to this coefficient?"

"......" Zhuo Ling replied seriously.

This question is not a little girl, Guan Debao was also a little surprised, and continued: "In polarization-maintaining fibers, the non-uniformity of the birefringence of the optical fiber can be ignored, and there can be obvious fast and slow axes, and its birefringence characteristics and differential group delay are simple to describe, usually expressed by vector formulas, you can use the three-dimensional vector description of Stokes space. ”

The tone is very aggressive.

Yan Sheng said: "Mr. Guan, Zhuo Ling is only a sophomore after all, and she has never been exposed to Stokes space, and this kind of vector description requires at least a master's level of matrix theory and numerical analysis, which is a bit difficult." ”

Guan Debao said: "Teacher Yan, this is the case in theory, but since Zhuo Ling has entered the laboratory, we should assume that she can learn the basic knowledge needed in scientific research, Zhuo Ling, what do you think?"

Chang Qing was very unhappy, little rabbit cub, isn't it that he can't get along with me, and was about to speak, Liu Chen kicked him lightly and shook his head, you took care of it enough just now, and now it is not suitable to come forward again.

"Teacher Guan is right, I really haven't understood this part thoroughly. Zhuo Ling lowered her head and replied, a little uncomfortable, but still able to remain calm.

"It's better not to put the content that you are not sure of, and then let's figure it out, vector description is the foundation, Chang Yuan, I think this topic is too difficult for Zhuo Ling. Guan Debao criticized, several other teachers felt that he was too nitpicky, scientific research is also progressive, like Bai Lei has been in the laboratory for many years and has made low-level mistakes, no matter how much criticism is overstated, it is really not too demanding when he first came in.

originally thought, after all, scientific research grows up in criticism, but Zhuo Ling was really taught a lesson, Liu Chen was still unhappy in his heart, a little bit of a calf protection emotion, Ling'er has really paid a lot, and it is also very good to do this step, there is really no need to criticize for the sake of criticism, or personal display, I don't have a good impression of Guan Debao, and I haven't seen him so strict with other students before.

In fact, Stokes space vectors are also very easy to understand, vectors must have directionality, and have their own set of operation rules, especially the use of legends to represent more intuitive. Liu Chen couldn't help but speak.

In the previous reports of the five people, Liu Chen had been sitting next to the Changyuan without saying a word, and everyone was puzzled from the beginning, and gradually ignored him, but he didn't expect such a young man to suddenly speak, and he said it in a very arrogant tone.

Guan Debao saw him jump out and speak, and he didn't get angry, what are you, Changyuan actually let me sit in the back row because of you, I am now criticizing other students, and you dare to jump out, you are simply ashamed, snorted lightly, and said with contempt: "Oh, so you have a deep understanding of Stokes space vectors, you might as well tell us about it." (To be continued.) )