A method, in an optical testing node, for establishing transmission parameters for optical communications, characterised in that the method comprising: transmitting an optical test signal through an optical network; analysing results of the transmitted optical test signal; and adjusting at least one parameter of said transmitted optical test signal based on the analysing, wherein said transmitting, analysing and adjusting are performed in an iterative manner, wherein the at least one parameter is a current modulation scheme, and/or a current light path length of the optical test signal; wherein upon analysing the results, if the optical path has not been found due to a lack of spectral width, the adjusting further comprises: selecting a new modulation scheme, from a sub-set of modulation schemes, such that the new modulation scheme has a higher spectral efficiency than the current modulation scheme; and thereafter, assigning the new modulation scheme as the current modulation scheme; and wherein upon analysing the results, if the transmitted optical test signal is not detected due to a low optical signal to noise ratio, the adjusting further comprises: increasing the current light path length by splitting the current light path or adding hops to the current light path; selecting a new modulation scheme, from a sub-set of modulation schemes, such that the new modulation scheme comprises a least amount of spectral efficiency from the subset of modulation schemes; and thereafter, assigning the new modulation scheme as the current modulation scheme. transmitting an optical test signal through an optical network; analysing results of the transmitted optical test signal; and adjusting at least one parameter of said transmitted optical test signal based on the analysing, wherein said transmitting, analysing and adjusting are performed in an iterative manner, wherein the at least one parameter is a current modulation scheme, and/or a current light path length of the optical test signal; wherein upon analysing the results, if the optical path has not been found due to a lack of spectral width, the adjusting further comprises: selecting a new modulation scheme, from a sub-set of modulation schemes, such that the new modulation scheme has a higher spectral efficiency than the current modulation scheme; and thereafter, assigning the new modulation scheme as the current modulation scheme; and wherein upon analysing the results, if the transmitted optical test signal is not detected due to a low optical signal to noise ratio, the adjusting further comprises: increasing the current light path length by splitting the current light path or adding hops to the current light path; selecting a new modulation scheme, from a sub-set of modulation schemes, such that the new modulation scheme comprises a least amount of spectral efficiency from the subset of modulation schemes; and thereafter, assigning the new modulation scheme as the current modulation scheme. selecting a new modulation scheme, from a sub-set of modulation schemes, such that the new modulation scheme has a higher spectral efficiency than the current modulation scheme; and thereafter, assigning the new modulation scheme as the current modulation scheme; and wherein upon analysing the results, if the transmitted optical test signal is not detected due to a low optical signal to noise ratio, the adjusting further comprises: increasing the current light path length by splitting the current light path or adding hops to the current light path; selecting a new modulation scheme, from a sub-set of modulation schemes, such that the new modulation scheme comprises a least amount of spectral efficiency from the subset of modulation schemes; and thereafter, assigning the new modulation scheme as the current modulation scheme. increasing the current light path length by splitting the current light path or adding hops to the current light path; selecting a new modulation scheme, from a sub-set of modulation schemes, such that the new modulation scheme comprises a least amount of spectral efficiency from the subset of modulation schemes; and thereafter, assigning the new modulation scheme as the current modulation scheme.